Weaver Ants_Building Behavior Simplexity Diagramming Forces

This research booklet is a study of animal architects and the building behavior of weaver ants (Oecophylla smaragdina). This investigation focuses on distinguishing the processes involved in the nest construction, such as bending of a leaf, weaving of silk and aggregation of ants to apply a pulling force upon the leaf. These mechanisms are therefore applied to a design and architectural scale - as an actuation principle for the transformation of a flat geometry to a three dimensional shape.

UniversitätStuttgart Stuttgart Universität

Institutefor forComputational ComputationalDesign Design Institute Institutfür fürComputerbasiertes ComputerbasiertesEntwerfen Entwerfen Institut

WINTER / 2016 - 17 / 49841 / ARCHITECTURAL BIOMIMETICS

Abstract

Weaver Ants

Building Behavior Simplexity Diagramming Forces

Course Name: Architectural Biomimetics Course Number: 311331800 Term/Year: Winter Term 2016/2017 Examination Number: 49841 Examiner : Prof.Jan Knippers, Prof. Achim Menges, Prof. Oliver Betz, Prof. James Nebelsick Tutors: Daniel Reist, Lauren Vasey Anja Mader, Evy Slabbink, Tobias Grun

Institute: Institute for Computational Design

Rasha Alshami Xun Li Sabīne Vecvagare Zuonan Cao Lilian Levinh

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Weaver Ants: Building Behavior Simplexity Diagramming Forces

Course Name: Architectural Biomimetics Course Number: 311331800 Term/Year: Winter Term 2016/2017 Examination Number: 49841 Examiner : Prof.Jan Knippers, Prof. Achim Menges, Prof. Oliver Betz, Prof. James Nebelsick Tutors: Daniel Reist, Lauren Vasey Anja Mader, Evy Slabbink, Tobias Grun Institute: Institute for Computational Design

Rasha Alshami Xun Li SabÄŤne Vecvagare Zuonan Cao Lilian Levinh

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Contents Chapter 01: Animal Architects _____Page 05 Chapter 02: Oecophylla smaragdina_____Page 17 Chapter 03: Experiments and Documentation_____Page 29 Chapter 04: Principles of Building Behavior_____Page 37

FIGURE 00_1: Weaver Ants (Source: Rasha Alshami, SabÄŤne Vecvagare, Xun Li)

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Chapter 01

Animal Architects

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CHAPTER 01

CHAPTER 01

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FIGURE 01_2: Weaver Ant Building Process (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li)

INTRODUCTION This study will explore the topic of builder animals, silk in nature, and abstract principles that could be implemented in an architectural scale. The research acquires information about processes in nature in order to apply them to built environment, distinctively to the fields of architectural design, engineering, robotics and fabrication.

FIGURE 01_1: Weaver Ants (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li)

The first part of our investigation is devoted to the study of silk as a material in general, and its uses in nature. We then advance to the subject of animal builders that use silk in their construction processes, as well as animals that modify their environment, in our case - using leaves to construct habitats. The study further approaches Oecophylla smaragdina as the selected role model for

building behaviour abstraction to architectural scope.

By doing extensive observation, experimentation and documentation of the behaviour of this ant species, our research adapts the findings to a building process technique.

According to D. W. Thompson the form of an object is a ‘diagram of forces’ (“On Growth and Form”, 1917), and using this notion our research maps the movement and applied forces during the building process of Oecophylla smaragdina colony. The analysis of these operations consequently lead us to abstractions in the field of design, robotics, fabrication, and structural efficiency for the applications in lightweight structures.

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CHAPTER 01

CHAPTER 01

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ANIMAL ARCHITECTS / HABITATS IN NATURE There are number of animals that exhibit spectacular building behaviour, whether producing their own building materials, or using their environment to construct habitats. Some of the most interesting animal builders are known to be caterpillars, wasps, spiders, ants and others.

In animal world moths are known for their intrinsic building projects. One of the examples is the palisade moth, which uses scales of its wings to build a circular fence on a leaf around its eggs. This fence protects the eggs until they hatch and are able to ascend the structure and disperse to feed on leaves. Another example is the whorl moth, which uses its own bristles and silk to build a protective dwelling. The caterpillar removes its stinging bristles and using silk attaches them on a branch in front and behind its pupation location, arranging them in series of whorls and creating a defensive fence. This construction allows it to pupate in a safe environment, where it can develop and emerge as an adult.

The paralastor wasp also exhibits interesting building behaviour. The animal excavates a tunnel, lining it up with mud and finishing the construction with a funnel that protects it against parasites. There is certain

relationship between the structure and ground against which it stands. The stem of the funnel is always roughly perpendicular to the ground, and the opening at the end of funnel is approximately 45 degrees from the horizontal connection. Paralastor wasps build similar structures, and the building process is strictly linear, with no simultaneous work between the animals.

The animal architects in general subdivide into solitary animals and social animals; where the building behaviours vary whether the building task is carried out by a single individual or there is a group work involved. Additionally, the building materials they use to construct their habitats also are important. Some of the animals use their surroundings - for example, building with mud, excavating tunnels, using leaves to construct their nests; while some employ their own produced materials (such as whorls, bristles and silk) to make structures. We found that the most widely used building material for animals is silk, and there are certain qualities and advantages to this material, which we chose to investigate further in relation to animal builders.

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SILK / NATURAL BUILDING MATERIALS In nature silk is produced mainly by spiders, caterpillars and ants. Silk is formulated in special glands to serve any variety of needs. Animals use silk for the purpose of predation (to catch other animals), reproduction and development (silk cocoons for caterpillars and cylindriform silk for spider egg case), defense (sensing the predators with transfer waves in spider webs), and habitation (web and nest building).

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There are certain properties of silk which make it an efficient building material, such as elasticity, adhesion, load bearing capacities, absorption and others. It can be stronger than steel and more elastic than rubber, as well as by changing its chemical component proportions - be sticky or slick as glass. Due to these properties silk is a topic of interest for the purposes of medical applications, as well as an inspiration for developing new materials for both small scale and large scale utilization.

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FIGURE 01_3: Palisade Moth Nest. (Source: photograph by Troy S. Alexander) FIGURE 01_4: Wasp Moth (Ctenuchinae) Caterpillar Using Whorls. (Source: photograph by Mark Moffett) FIGURE 01_5: Paralastor Wasp Funnel. (Source: photograph by Linda Rogan)

inhabitation. They construct nests and use silk as a catching device. Out of caterpillars, the silk is produced at larva stage, where it is needed for inhabitation and metamorphosis. An interesting aspect is that one of the most natural animal builders - ants, with their ant-hill and ant-cave building techniques, are also known to produce silk. There are two species of ants - Melissotarsus emeryi and Oecophylla smaragdina which produce silk for building purposes. The first one is known as the braiding ant, which appropriates silk to enclose holes in trees and construct habitats. The second one is the weaver ant, for which the silk is produced by their larvae, and adult ants use the larvae as means to stitch leaves together and assemble nests. This process of team work was of interest for us to explore further in our research in terms of building behaviour.

Silk producing animals use it for different operations.

Araneidae spiders create silk for capturing prey and FIGURE 01_6: Silk as Habitat for Metamorphoses. Cocoon of the Bombyx Mori Moth.

FIGURE 01_7: Silk for Predation. Spider Web. FIGURE 01_8: Silk for Habitation. Caterpillar Nest.

FIGURE 01_9: Spider Silk Glands Under Microscope.

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CHAPTER 01

LEAF MANIPULATING ANIMALS / USING ENVIRONMENT FOR CONSTRUCTION There are multiple animals that use their surroundings to build their habitats. Since we were quite interested in the building process with silk, the subject of combining silk building and the use of existing environment was of great interest. There are a few animals that use silk to build with leaves. We chose to compare three different species in their behavior in terms of manipulating leaves to create habitats, while using silk as their construction element.

The studied animals are caterpillars (leaf roller caterpillars, e.g. Caloptilia serotinella), beetles (leaf roller weevil Attelabidae) and ants (weaver ants, e.g.

Oecophylla smaragdina). Our research lead us to an additional comparison of the beetle Attelabidae with the aforementioned Caloptilia and Oecophylla, due to the similarities in construction process.

The leaf rolling caterpillar in its building procedure starts with the rolling of a leaf, and then continues the process by fastening it with silk. The purpose of this construction is habitation, reproduction and protection.

The weaver ants divide the process of their habitat development into teams of tasks, where some of the ants are bending a leaf, while others are stitching them together with the use of their larvae which produce silk.

The beetles do not use silk in their building process, however they manipulate the leaf on their own and produce a rolled structure in the end.

We studied these animals in terms of their habitat construction, the reason for this building behaviour, as well as factors for choosing the building material - in this case, the leaf.

LEAF ROLLING CATERPILLAR / Caloptilia serotinella Leaf shelter-building caterpillar in its process of building chooses a host tree, in which it rolls, folds or ties together leaves to form an enclosure. In this habitat they feed and rest, and the shelter protects the resident caterpillars from predators and solar radiation. The shelters may also serve as overwintering or pupation sites. Leaf shelter-builders do not manipulate leaves directly but use their silk to draw plant surfaces together.

The strands of silk are produced by rhythmically swinging the anterior half of the caterpillar’s body through successive arcs, while drawing a continuous thread of silk from its spinneret. The strand is securely fastened to the substrate by spreading the thread at the attachment point. Axial retraction of the fixed strands causes the apex of the leaf to bend toward the relatively stiff midrib, drawing the lower leaf surfaces together.

When on a leaf, the caterpillar typically mounts the leaf by walking along its length. The caterpillars often lay a thin layer of silk on the midrib before initiating leaf rolling. They also chew small, closely spaced, shallow slits in the midrib and sometimes remove small sections of tissue from the leaf blade immediately adjacent to it. Larvae continue to lacerate the midrib periodically throughout the leaf rolling process (Fitzgerald and Clark, 1994).

Afterward the caterpillar constructs a new column of silk by attaching strands between the midrib and the exposed upper leaf surface at an average angle from the midrib. It continues to spin intermittently in this manner until the leaf is turned through. The caterpillar then closes the ends of the roll by drawing the edges together with silk and, in the process, encloses itself inside. During the rolling process the caterpillar elevates itself by climbing onto the silk strands, then rhythmically swings the anterior portion of its body from one attachment point to another.

The laceration of the leaf is done in order to weaken the structure due to both direct mechanical damage and subsequent loss of turgor. Larva initiates the leaf rolling by laying down a band of silk strands relatively parallel to the midrib, 10- 15 mm from the apex of the leaf.

Each strand (the length of silk between two attachment points) extends from a point on or near the midrib to another point on the midrib or on a flat surface of the leaf nearer to the apex. Between episodes of rolling, larvae feed within the developing shelter or add new lacerations to the midrib.

When rolling the leaf, caterpillars stretched strands to a much greater extent. Unlike the slightly stretched strands used to seal the roll ends, part of the length of strands spun to roll the leaf developed helical coils when the tension on the strand was removed, causing them to behave to some degree like retracting springs.

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FIGURE 01_10: Leaf Rolling Caterpillar. Process of Rolling.

FIGURE 01_11: Leaf Rolling Weevil. Finished Nest.

FIGURE 01_12: Weaver Ant and Nest.

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FIGURE 01_13: Leaf Rolling Caterpillar Habitat.

FIGURE 01_14: Leaf Rolling of Oak Leaf.

FIGURE 01_15 - 01_16: Leaf Rolling Process.

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CHAPTER 01

CHAPTER 01

In the second phase, rolling up the leaf involves following up triangular lines. After rolling up the apical part of the leaf two or three times, the female weevil bores holes and oviposits in them from one to three eggs. During the rolling process, the male visits frequently to ensure protection of the construction, however it does not participate in the building process. The completion of the rolling process takes an hour and forty minutes to two hours. The last step is to cover the cradle by reversing the folded blade, drawing and twisting the inner side.

LEAF ROLLING WEEVIL / Attelabidae The leaf rolling weevil is known for the species special care of their descendants. All female species Attelabidae create cradles from the leaves of their host plants. A detailed study has been made on their construction process of the cradle (Park, Lee, and Park, 2011).

The female Attelabidae inspects the size and form of the leaves of their host plants, and cuts them. The cutting method is based on the beetle’s perception and strategy for the cradle formation. The location, length and form of the cutting lines are based on intrinsic approach to the building process. The cutting of the leaf blocks the passage of water through the midvein, not only withering the leaves, but also making it easier to roll the leaf blades in reverse. The cradle formation of the weevil is divided into two phases. The first phase involves inspection of the leaf, cutting, nibbling and attaching of folded leaf. The second phase is rolling, oviposition and finishing the construction (Fig. 01_22).

During the first phase the leaf inspection is made by walking around the leaf to observe its size, freshness and absence of insects. Then the female weevil moves to the margin of the leaf and starts cutting. The method of cutting varies between cases and depends on the species. There are seven distinct leaf cutting patterns (Fig. 01_17). The first one is the non - cutting type, in

which no cutting is involved in the building process.

The second pattern is created by cutting the leaf margins from both sides towards the midvein without breaking it. Then there is a case where only one cut is made, in one direction which stops at a point slightly beyond the midvein of a leaf blade. The next cutting patterns distinguish the shape of the cut; there is straight cutting type (cutting in both directions, breaking the midvein straight to the end), L- shaped cut (cutting in one direction, turning nearly at a right angle to the basal part without breaking the midvein), and quasi- Lshaped cut (in one direction, turning nearly at a right angle to the basal part, sopping at a point beyond the midvein of a leaf blade, making a path similar to the letter L). The last cut type is curved cutting, which starts from one margin of a leaf blade, then makes a shape of the letter J, crossing the midvein and stopping at the other margin of the leaf blade. After cutting the leaf, the weevil moves on to the other side of the leaf and nibbles along the midvein. Nibbling withers the leaf and makes it easier to roll. Once the leaf begins to wither, the weevil rolls the tip of the blade with the midvein upwards and completes a cylinder shape roll. This folding is the basic strategy for making the weevil’s cradle.

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01_19 01_20 01_21

6. FINISHING (HALF-OPENED FOLD)

5. AFTER OVIPOSTING, REMAINING LEAF ROLLS UP

4. ROLLS UP THE LEAF NO-CUTTING TYPE

BOTH SIDES CUTTING TYPE

L- SHAPE CUT TYPE

SINGLE-CUT TYPE

QUASI L- SHAPE CUT TYPE

STRAIGHT-CUT TYPE

7. COMPLETION

CURVED CUT TYPE

3-1. BITES THE LEAF

1. INSPECTION OF LEAF

2. CUTTING OF LEAF

01_22 FIGURE 01_17: Different Types of Weevil Cutting. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li)

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FIGURE 01_18 - 01_21: Leaf Rolling Caterpillar. Process or Rolling.

FIGURE 01_22: Complete Process of Habitat Making. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li)

3-2. FAILURE AT CUTTING

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CHAPTER 01

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WEAVER ANT / Oecophylla smaragdina The weaver ant gets its name from the process of their nest construction. The ants build their nest by using leaves, folded and fastened together to form enclosed habitats. The construction process starts with a choosing a tree branch which is suitable for the size of the colony. Then the ants spread around the leaves, and pull on the tips and edges of the leaves.

Ants aggregate themselves around each other to form chains pulling leaf edges, and attempt to connect or bend the leaves. When the desired shape is achieved, it is secured together. The fastening system used is silk,

produced by the Oecophylla larvae. The major workers hold larvae and move them to weave between leaves.

This nest building process is highly dependant on the size of the ant colony, as well as the chosen leaf or branch. A weaver ant nest can be made from one leaf, as well as from connecting two or more of them. The bending direction can be both perpendicular or parallel to the major leaf of the leaf. The rules of weaver ant construction behavior will be analysed further in later chapters.

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CONCLUSION The three studied animal types have their own methods of construction. Their task is mainly with the aim to inhabitation, and these animals either roll the leaves or bend them. The means of securing these rolled or bent structures is either by using silk as adhesive or folding and biting certain parts to secure them. Two of the chosen role models achieve their tasks as solitary LEAF-ROLLING CATERPILLAR

FIGURE 01_23: Weaver Ant Nest Building Process. (Source: Rasha Alshami, SabÄŤne Vecvagare, Xun Li)

animals, however weaver ants divide the building assignment between the members of the colony. We found the social building behavior interesting in terms of potential abstraction to architecture scale, and we could see potential for either robotic or construction performance.

LEAF-ROLLING WEEVILS

WEAVER ANTS

HABITAT CONSTRUCTION 1. inspecting (on the leaf) 2. cutting 3. attaching silk 4. folding 5. securing 6. rolling

HABITAT CONSTRUCTION 1. inspecting 2. cutting 3. rolling

HABITAT CONSTRUCTION 1. inspecting 2. forming a pulling chain of ants 3. biting 4. rolling

REASON - protection

REASON - reproduction - protection

REASON - care for offsprings

FACTORS FOR LEAF CHOOSING - initiated cutting through walking around the circumference of the leaf

FACTORS FOR LEAF CHOOSING - size, shape of the leaf - structure of females recognition process

FACTORS FOR LEAF CHOOSING - size, shape of the leaf - protected areas

FIGURE 01_24 - 01_26: Building Process. Weaving, Pulling and Aggregating. (Source: photograph by Mark W. Moffett)

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Chapter 02

Oecophylla smaragdina

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CHAPTER 02

CHAPTER 02

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BUILDING PROCESS / AGGREGATION

WEAVER ANTS Subsequently after considering varied animal architects and their habitats, particularly ones using leaves in construction, we found weaver ant behaviour particularly interesting. The unique aspect of their building process is the use of larval silk in the securing formed nest chamber. Weaver ants belong the ant genus Oecophylla

(subfamily Formicinae), which distinguished two closely related species: Oecophylla longinoda and Oecophylla smaragdina. Both of the species are what we know as weaver ants, and in this research we will look further into O. smaragdina as a role model for construction behavior that could be adapted to architectural field.

ADHESION

AGGREGATION weaver ants aggregate in optimized system to adapt to the leaf shape they want to bend

arolium is used for adhesion, support and strength

Aggregate formation is one of the most frequently observed phenomena in a wide range of behavior types demonstrated by social insects. A particular type of aggregation can be defined as self-assembling, which occurs when individuals grip on to each other (Rettenmeyer, 1963; Schneirla, 1971; Gotwald, 1995).

The Oecophylla ants are known for their ability to form two types of chains. The first type allows them to bring themselves over empty spaces, for example, between two branches or leaves. The second type is achieved with the aim to bind the leaves together during the construction of a nest. The individual ants hold together and form a collective structure. They can achieve these chains due to their strong, well developed and adhesive arolia under the tarsus. The chain formations are constructed by a progressive attachment of workers holding on to each other by their legs and remaining motionless.

SILK WEAVING

weaving is the last step in the building process, depends on the ant aggregation and the leaf shape

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BUILDING PROCESS / PROPERTIES In this chapter we will present certain characteristics that aid the weaver ants in the nest construction process.

These properties are aggregation, adhesion and silk weaving.

In terms of aggregation - weaver ants form chains to pull and bend the leaves they are building with. The chain formation depends on the leaf shape and desired outcome. If the leaf is broader than the length of the ant’s body, or when two leaves are to be pulled together across a space, the worker form bridges between the joining points. After forming the chain, some of the ants climb onto their neighbors backs and pull the chain backwards, shortening it and essentially pulling the leaves together (or leaf edges). When the desired shape is achieved, some ants remain on them. They use their legs and mandibles to hold the leaves in place while the structure is secured with silk.

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ant’s leg there is a specialized appendage that is called tarsus, and allows them to attach to smooth surfaces.

The tarsus includes claws for movement through rough terrain, as well as a flexible pad - arolium, which helps it adhere to surfaces. The arolium is a flat flexible cuticle, and coated with viscous secreted fluids, which permits it to act similar to a wet suction cup.

The last characteristic that is greatly involved in the building process is the use of silk to secure the structure. The weaver ant workers approach the seam of the leaves that have to be joined together, and hold larvae, moving their heads against the seam in a weaving motion, which cause the larvae to excrete silk.

Since the silk produced by larvae is used externally, the ants pupate without a cocoon. The weaver ant workers maneuver between the leaves to bind them together in strategic places.

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Another property that greatly aids the weaver ants in their building process is the adhesion. The tips of the

FIGURE 02_1: Weaver Ant Properties of Construction. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li)

FIGURE 02_2 - 02_3: Ant Aggregation for Leaf Pulling and Protection of Queen. (Source: photograph by Mark W. Moffett) FIGURE 02_4: Weaver Ants Reaching Across Space.

FIGURE 02_5: Weaver Ant Bridge Across Space. (Source: photograph by Adhi Prayoga)

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CHAPTER 02

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BUILDING PROCESS / ADHESION After the creation of the weaver ant elaborate woven hives from plant leaves, the weaver ants frequent the routes to gather payloads home. The routes bring them over soil, up the bark of the trees they inhabit, and across undersides of smooth leaves. Both the travel and carrying of items are due to their evolved tarsus, and the weaver ants can grip with both claws and suction.

When moving in hard conditions (vertically or on underside of leaves), the weaver ant plants its foot and applies a dragging force inwards on its tarsus, allowing the arolium to expand passively and increasing the

suction contact with the surface. Ants can carry heavy loads over smooth surfaces due to this mechanism of suction-adhesion. Weaver ant workers can support weight equal to 100 times that of their weight. The suction is extremely advantageous since it prevents any detachment in case of unexpected jostling. Additionally, if only a little pressure is applied to the arolium, it does not expand as significantly, and this permits the ant to move at a faster pace when no load is carried (Michael Bok, 2010).

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02_11 02_7 02_12 02_6

BUILDING PROCESS / SILK WEAVING The last property of building that weaver ants possess and which allows them to build their elaborate nests is the ability to weave silk. When the ants have spread around the leaves they will inhabit, they begin to pull on the tips and edges of these leaves. After each successful step of pulling a segment of a leave, the nearby worker join the task, gathering larger group of ants pulling on the same part of leaves. The aggregated ants pull simultaneously. If there is a larger leaf or two leaves are to be joined across a space, a chain and eventually a bridge is formed that achieves this pulling task. When the leaves are in their desired position, then begins the silk attaching.

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As previously mentioned, the silk of weaver ants is produced by their larvae. The workers move the larvae

back and forth between the seams of the leaves, in a weaving motion. “The adults carry larvae in their jaws and squeeze them gently so that the larvae secrete a drop of silk on one end of the leaf edges. The ants then carry the larvae along the entire length of the leaf edges, squeezing as they go, using the larvae like living bottles of glue, until the edges of the leaves are stuck together from end to end� (Shuker, 2001:191). The larvae release threads of silk, and it is produced by gland openings below their mouths. After applying thousands of threads, the seam is strong enough to hold the leaves in place. Silk is also applied to the circular entrances of larger nests, when more leaves are joined in a greater structure.

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FIGURE 02_6: Ants Traveling Across Challenging Surfaces.

FIGURE 02_7 - 02_9: Weaver Ant Gripping Mechanism: Arolium and Lifting Force. (Source: Thomas Endlein)

FIGURE 02_10: Weaving Process. (Source: image by Norton) FIGURE 02_11: Weaver Ant Carrying Its Larva. (Source: photograph by Jamie Mitchell) FIGURE 02_12: Weaver Ant Weaving. (Source: photograph by Alex Wild)

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CHAPTER 02

RECIPROCITY

ANIMAL BEHAVIOR / HIERARCHY AND RECIPROCITY There are two distinct fields of study we distinguished in terms of weaver ant behavior. The first one is the hierarchical division of the building tasks, and the other is the reciprocal relationship between the ant size and amount to the bending / folding properties.

HIERARCHY Oecophylla smaragdina has a distinct caste system and the numbers of individuals in each caste reflect their respective functions which contributed to the success of their colony. The main social unit of the weaver ants is the colony. It consists of potentially up to 500 000 female workers, which are the progeny of a single queen.

There are three forms of an adult female - the enormous queen, an extensive population of major workers, and lesser community of minor workers. The sizes of these weaver ant colony members depend on the tasks they have to achieve for their community. Eggs, larvae and pupae can also be counted as a part of the colony.

The function of each individual within the colony is based on the caste system and division of labour. According

to Holldobler and Wilson (1977), the major workers who are the general laborers are fairly large averaging about six millimeters. The responsibilities for the major workers include foraging and nest construction. Within the class of workers, there are more aggressive ants - the soldiers, which bite intruders and release formic acid from their poison gland at any disturbance of the nest or sign of threat. The major workers always aggregate around the queen. They grasp her with enormous strength, at times it is noted that she is held mid air in the center of the nest interior. The major workers feed the queen, once a minute regurgitating liquid meal into her mouth.

As mentioned previously, the nest forming process starts with an ant or a chain of ants bending the leaves and securing them in a place, while workers adhere the leaves together using silk produced by their larvae.

However there is a relation between the ant size and reach to the leaf size that corresponds to the method of nest construction. This relationship is based on a ratio which is apparent in the adaptive forming process of the nest.

Further in this chapter we diagrammed the most common nest construction types, as well as some rare

cases. For example, if the nest is built from smaller leaves, a smaller chain of ants is required. When the span between two leaves is beyond the reach of a single ant, a chain is formed by the workers, grasping each other by their petioles (waists). If two or more leaves are added to the nest, the ant chain adapts to the space between to form a pulling force that aids them in the bending process. In this particular case there might be added a third leaf, which would enclose the first two leaves and act as a cover or reinforcement. All of these cases are thus presented in diagrams in the next pages.

The weaver ant queen lays up to hundred eggs per day.

The eggs are extruded from the queen’s oviduct, and major workers move them to special piles. The smaller minor workers are responsible for the care of the eggs, as well as feeding and washing of the tiny larvae when they hatch from them. When the larvae develop to their maximum size, the care for them is shared between the major and minor workers.

TEAM T1 = G + T2 where T2 =I1 +I2

GROUP 02_13

TEAM INDIVIDUAL

INDIVIDUAL

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T1 = build nest; G = pull leaves together; T2 = glue leaves together; I1 = move larva over seam; I2 = produce silk

02_14 02_15 FIGURE 02_13: Weaver Ant Hierarchical Structure of Tasks. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li) FIGURE 02_14: Weaver Ant Hierarchical Sizes. (Source: Antstore, 2017) FIGURE 02_15: Weaver Ant Sizes. (Source: J.B. Slater, J. S. Rosenblatt, Charles T. Snowdon, T. J. Roper, M. Naguibah, 2005)

FIGURE 02_16: Weaver Ant Nest Building Types. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li)

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CHAPTER 02

CHAPTER 02

single ant behaviour width = reach

multiple ant behaviour width = reach x nr of ants

top view

top view

50 - 55 %

task sequence: 1. join two or more leaves side by side 2. add additional leaves by adding them from the bottom

section view

section view

reach 1.

1.

reach

1.

45 - 50 % 2.

width of the leaf

50 - 55 %

45 - 50 %

multiple ant behaviour

width

multiple ant behaviour width = reach x nr of ants

top view

top view

reach

50 - 55 %

section view

25 %

75 %

45 - 50 %

width of the leaf

section view

50 - 55 %

45 - 50 % 25 %

FIGURE 02_17: Weaver Ant Single Leaf Nest Building Types. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li)

75 %

FIGURE 02_18: Weaver Ant Two Leaf and Unusual Nest Building Types. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li)

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CHAPTER 02

multiple ant behaviour width = reach x nr of ants top view

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02_21

in this case: - more silk needed - more workers needed

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02_23

FIGURE 02_19: Weaver Ant Larger Nest Building Type - Rare Case. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li)

FIGURE 02_20 - 02_21: Weaver Ant Nest Types.

FIGURE 02_22: Weaver Ant Larger Nest Type.

FIGURE 02_23: Weaver Ant Nest With an Opening. (Source: photograph by Raghu Mohan)

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Chapter 03

Experiments and Documentation

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CHAPTER 03

CHAPTER 03

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EXPERIMENTS / SET-UP From the outset of this research, our focus was first to understand the aggregation mechanism through which ants assemble themselves to pull the leaves, and second - to understand the forces shaping the leaf in terms of the resulting final product. Accordingly our first endeavour was to obtain an Oecophylla smaragdina colony and execute an experiment to record and analyse in order to understand the building process of a weaver ant nest.

We managed to acquire a colony consisting of one queen and approximately thirty Oecophylla workers from Borneo. The ants are sensitive to outside factors especially humidity and temperature, therefore the task of relocating them to our observation area proved to be difficult. The fluctuation of both factors was kept to a minimum during transportation, and the ants were placed in a tank which already had moisture and temperature within the ideal range. However we learned that relocation of a colony even under controlled parameters leads to an anxiety, therefore it was advised to allow the colony adapt to their new environment for a week before performing any experiments.

A colony of thirty ants is considered a relatively small one; a full sized colony may have more than 500 thousand individuals (Lokkers, 1990). The obtained colony was transported with a completed nest fully intact, therefore the ants did not construct any new habitats during the first weeks of our observation. Considering

that developing O. smaragdina colonies have a low survival rate, we postponed any experiments for two weeks to let the colony stabilize.

An important aspect was the documentation of the experiments. To inspect any developments of the ant building behavior and nest construction we recorded the enclosure using GoPro camera (with time-lapse, taking a photo every 60 seconds). The camera recorded the Oecophylla colony 24 hours per day during the experimentation phase.

ENVIRONMENTAL SETUP Our research in the O. smaragdina building behavior was held in an observation tank of size 80 x 40 x 50 centimeters. Within the tank a host plant was placed for the weaver ants to build their nest in. The plant was seated in a plastic tub in the center of the tank to separate the plant from surrounding water, which formed a barrier to prevent the ants escaping the tank.

A light bulb and humidifier were used to regulate the appropriate light, heat and humidity for the colony.

The ants were mainly fed with bug jelly and crickets.

Live crickets were not fed as the colony was too small to effectively overpower and dissect them; continually halved crickets were given to satisfy the colony’s protein needs.

03_3

03_2

03_4

FLEXIBILITY OF OECOPHYLLA NESTING BEHAVIOUR It has to be noted, that Oecophylla species display variability in their nesting behaviour. Weaver ants are best known for their constructions of leaf nests, however, under certain conditions weaver ants have been found to also accept alternatives as nests. For instance, nests are vulnerable to heavy rain and wind.

Accordingly during the rainy season in Thailand O. smaragdina colonies would also accept plastic bottles as nests even if suitable leaves were available. The bottles were abandoned in favor for leaf nests after the rainy season. Also O.longinoda has been reported to build its nests leeward during the time of monsoon (J. Offenberg, 2014).

During our observations of the obtained weaver ant colony, after the first weeks of relocation to the observation tank, the colony moved to the edge of the tank, where they started to weave a nest in a corner.

This, as we found, was due to the inability to adapt to the leaves that we provided the colony with during the FIGURE 03_1: Weaver Ant Building Process. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li)

beginning of our study (based on a previous research we were providing the weaver ants with various papers of leaf shapes). We found this behavior of great interest in terms of adaptive behaviors of animal builders. As previously mentioned, Oecophylla species show certain compliancy towards environmental conditions and can display opportunistic behaviour.

The different responses to altered environmental conditions may be of interest for further research as they can give further insight into the ant’s construction behaviour. However we did not subject the ants to any outside stress factors in order to not endanger our small developing colony. We secured the their environment to allow them further nest building with more appropriate leaves. Since our main aim was observing the basic leaf-nests construction they were held in a stable environment within ideal parameters, to avoid atypical nesting behaviour.

FIGURE 03_2 - 03_3: Use of Artificial Nests by Weaver Ants. (Source: O. Joachim, 2014) FIGURE 03_4: Experiment Setup Container. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li)

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CHAPTER 03

CHAPTER 03

OBSERVATIONS / BEHAVIOR AND BUILDING PROCESS From our experiments and observation we documented bending and weaving of two leaves. The weaver ants assembled this habitat in an unexpected manner. As noted in previous chapter, the joining of two leaves to form a nest is usually done by pulling the leaves inwards and together. However, in our experiment the leaves were joined in a technique that resulted in a covered structure. Research suggests that ants construct their nests in such a way in case of external threats. Some motion and frequent filming might be the reason for this behavior. The ants also briefly relocated to nest beneath fallen leaves at the bottom of our observation tank, which acted as a temporary protective shelter that they did not have to weave to utilize.

During the relocation from one nest to another, the workers carried their queen. We found out that the enormous queen is unable to scale vertical obstacles,

and usually in nature the workers help to transpose it.

This movement also allows the workers to fully protect the queen from any outside threats, as they assemble around the queen during all periods of relocation.

Throughout our experiment we needed to clean and change their environment, to ensure appropriate surroundings for their nest building processes.

Therefore, at times we had to reposition the colony in a plastic container, while changes were made to the bigger tank. While in the container, the ants grouped themselves in two corners of the container. As they moved around, ants one by another eventually joined the larger group. This proves that weaver ants relocate and collect themselves around groupings of ants, which is intrinsic for their nest building process and pulling chain formation.

03_9

03_10

03_5

03_12 03_6

03_11 03_7 03_13

03_8

FIGURE 03_5 - 03_8: Observations: Relocation of Queen, Feeding, and Weaving. (Source: Rasha Alshami, SabÄŤne Vecvagare, Xun Li)

FIGURE 03_9 - 03_13: Weaver Ant Nest Building Process. (Source: Rasha Alshami, SabÄŤne Vecvagare, Xun Li)

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34

CHAPTER 03

CHAPTER 03

03_14

03_15 03_18

03_16

03_17

03_19

FIGURE 03_14 - 03_15: Ant Aggregation for Defence During Move to New Habitat. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li) FIGURE 03_16 - 03_17: Ant Aggregation Around Queen During Relocation. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li)

FIGURE 03_18 - 03_19: Weaver Ant Nest. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li)

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36

37

Chapter 04

Principles of Building Behavior

38

CHAPTER 04

CHAPTER 04

LEAF / ANT AGGREGATION The ant Oecophylla is the only species that uses the deposition of larval silk and manipulation of leaf substrate to form a nest. The final form of the weaver ant nest is a material organization which responds to the internal factors of the used leaf and external conditions of the environment, in terms of ant pulling force and weaving of silk. Therefore three interrelated systems can be distinguished: the leaf as a material and geometry; ant aggregation as an external mechanical system, e.g. material assembly; and construction technique.

Understanding of the relation between these systems could eventually allow to insight into the construction behavior as a multi-performative system, which satisfies several objectives and achieves an optimal result.

LEAF The leaf selected by the ant is the first component of this performative system. Construction begins by workers surveying potential nesting leaves. The next step is to move the edges with their mandibles, grasping and attempting to pull the edge of the substrate. The bending of the leaf depends on its size, geometric arrangement or the overall external shape, and material patterning in terms of topology or internal structure.

parameters for sensing: 1. - edge lowest angle 2. - size of the colony 3. - stiffness

along the sides of the tip to facilitate pulling it forward.

Oval or elliptical leaf are preferred due to the relation to the ant pulling arrangement.

ANT AGGREGATION Once the first aggregation of ants starts, more ants joint the effort. As the building process progresses, other workers nearby join the task. There are two types of chains constructed - pulling chains and hanging or bridging chains. The first one is formed with the task to bring two leaf surfaces together, while the other is to reach across a gap between substrates (Bochynek and Robson, 2014). Each ant that participates in the nest building either selects a site beside the first individual or grips the body of the preceding worker to form a pulling chain. There might be multiple chains working in unison to draw together larger leaves in broader nest constructions. When the colony size is larger then the probability of a worker joining the effort of a pulling task is higher. The ants aggregate in a shape that resembles a triangle, and as the base of it increases due to inward dragging, additional individuals form a new pulling chain parallel to the existing one.

The shape of the leaf is of great importance. A worker ant always starts at the tip of the leaf with bites reoccurring

GLOBAL SHAPE

ASSEMBLY

LOCAL GEOMETRY

APPLYING FORCE

2.

3.

1.

4.

2.

1.

3.

2.

4.

1.

3.

04_1

FIGURE 04_1: Pulling Chain Formation. (Source: Thomas B. Simon K. A. Robson, 2014)

FIGURE 04_2: Pulling Formation for Leaf Bending. (Source: Rasha Alshami, SabÄŤne Vecvagare, Xun Li)

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CHAPTER 04

CHAPTER 04

SENSING AND SCANNING The general form of the pulling chains is triangular with equal sides. This triangle can be drawn within an equilateral form. The exerted pulling force is always nearly perpendicular to the base of the triangular ant formation base. Once there is a sufficient number of ants performing the tugging motion, the perimeter of the substrate is pulled towards the center of the leaf. This creates a potential nest chamber.

The mechanics of the pulling chain system are of great importance in terms of direction of the force exerted, the triangular form of ant aggregation and the mechanics of hinging between the ants. The force is dependent on how many ants participate in the task, and the mechanics of hinging could be regarded as an ant grasping the ant in front of it to control the direction of pulling. These aspects are highly dependant on the size and shape of the leaf and its surface. Once the leaf is bent in a desired form, the pulling chain locks itself in a rigid

arrangement while the workers use their mandibles to carry the larvae to the seams that need to be joined. If the chosen form is not achieved, then the ants change the direction of their grasp to modify the forces applied to the formation. They perform this until achieving a final form. The understanding of these principles could be beneficial in design of a structure that can adapt its shape or stiffness based on an information received by its context.

The researching of geometrical states that have the capacity to deform or expand into a desired form can lead to a comprehension of structural adaptability in relation to actuation forces. There is an inclination of a local geometry affecting the global one. The goal would be a system which integrates dynamic or kinetic solutions which are adaptive to changes given by its surroundings; and has a mechanism that adapts to the information given by the context.

After the understanding of the weaver ants building behavior and construction methodology, there is a need to investigate the application of such systems in terms of applicability to design. We were generally interested in adapting principles for a fabrication method where the application of a controlled pulling force can actuate a two dimensional geometry in a spatial three dimensional shape. A relation can be made to a cable net structure with a flexible geometry and certain topology. The tensioning of the net structure would be via the application of an external pulling force, making it kinetic in its assembly. With the pull of a cable within the structure, the geometry would tension and roll into a spatial form from state.

Several iterations of the cable net topologies were generated, where spatial form is actuated by pulling force. The final shape is determined by the original size of the flexible geometry and the connections within it. The visualized prototypes focus on exploring the differentiation of connections in relation to the geometries, abstracting the ant movement observed from the experiments. Furthermore we explored how the force and pulling direction (as well as its direction) influences the outcome of the final design.

The physical tests with the net structures investigate some aspects that greatly relate to the Oecophylla smaragdina nest construction process. The major conclusion from these iterations of models is that the overall final three dimensional form is dependant on the original geometry, its size, the topology of cable network, connections, as well as the position, direction and magnitude of the pulling force.

FIRST ANCHOR POINT IS THE SMALLEST ANGLE

ANT AGGREGATION

PULLING FORCE

CHOOSING A LEAF TO ADD TO STRUCTURE

CHOOSING THE NARROWEST ANGLE TO PULL; AGGREGATING ON THE LEAF

WEAVING

DEFINITION ant position = smallest angle ant position = a

ASSEMBLY RECONFIGURATION

ant aggregation = a1, (b2+c2), (d3+e3+f3), ...

If first migration: ...first edge = p ...fixed joint = length (ant aggregation - 1) ...direction = directional vector starting from (a/2) ...movement = (ant aggregation + direction) - fixed joint else: *large colony* ...closest leaf = closest edge ...reconfiguration = directionality + joints ...formation = triangle(a ^ {2} + b ^ {2} = c ^ {2}) ...connection = first migration weaving

FIGURE 04_3: Analysis of the Building Process. (Source: Rasha Alshami, SabÄŤne Vecvagare, Xun Li)

WEAVING

FIGURE 04_4: Sequence of Adding Leaves to Ant Structures. (Source: Rasha Alshami, SabÄŤne Vecvagare, Xun Li)

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CHAPTER 04

PULLING FORCE

FIXED MOVEMENT

MOVING X-DIRECTION

MOVING Y DIRECTION

02_13

PULLING FORCE FIXED MOVEMENT

02_13

02_13

PULLING FORCE MOVING IN X DIRECTION

02_13

PULLING FORCE MOVING IN Y DIRECTION

FIGURE 04_5: Pulling Process in Weaver Ant Building Sequence. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li)

FIGURE 04_6: Physical Models Exploring the Actuation Concept. (Source: Xun Li)

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CHAPTER 04

CHAPTER 04

45

CONCLUSION This research was carried out within the approach of biomimicry, where developments and inventions are based upon structural understanding of how nature and its processes operate. The focus of this study was the building processes of animals that produce silk and use leaves in their constructions. The Oecophylla was investigated and documented further due to it satisfying both of these criteria, as well as having a potential for relation to the scale of architecture and design.

To better understand the nest construction of the weaver ants, this research explored the general behavior of weaver ants, their hierarchical building process and the technique of their nest construction. This was done in order to attempt to abstract principles for architectural scale and tests in physical models. The analysis of the nest construction allowed us to identify how a flexible form can be modified by a temporary kinetic structure with movable joints to reach a desired form.

As an abstraction the flexible form is considered the leaf, movable joints - the ant aggregation, and form - the complete nest. Finally, once a desired shape is reached, it can be fixed via a binding material - in terms of the research role model - silk.

A major conclusion of this research is that the complexity of the nest building process can be understood as the layering of several simple processes. In other words, the complexity and intelligence of the construction system lies not in how clever the system is, but how the underlying subsystems actually relate to each other exploration, aggregation and weaving. The complexity of the relationship between these subsystems allows the creation of technique that far exceeds the material and structural limitations of each component. Therefore it can be say that the building process of Oecophylla smaragdina is in a way both simple and complex.

The understanding these building systems through analysis allowed us to abstract the construction sequence and produce a series of experimental models that exemplify and emulate the nest building process.

There is a potential for future explorations of such models that could lead to creation of morphing structure that is environmentally responsive and formally changeable.

As such, a hybrid structure can be constructed by merging the aforementioned three systems where global shape can affect local scale and vice versa, therefore establishing a new design paradigm.

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CHAPTER 04

CHAPTER 04

IMAGE CREDITS FIGURE 00_1: Weaver Ants (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li) FIGURE 01_1: Weaver Ants (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li) FIGURE 01_2: Weaver Ant Building Process (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li) FIGURE 01_3: Palisade Moth Nest. (Source: photograph courtesy Troy S. Alexander, Tambopata Research Center; http://voices.nationalgeographic. com/2013/09/06/what-created-this-mysterious-picket-fence-in-the-amazon/) FIGURE 01_4: Wasp Moth (Ctenuchinae) Caterpillar Using Whorls. (Source: photographed by Mark Moffett; http://www.mindenpictures.com/search/ preview/wasp-moth-ctenuchinae-caterpillar-places-whorls-of-its-own-long-stiff-hairs/0_00127416.html ) FIGURE 01_5: Paralastor Wasp Funnel. (Source: photographed by Linda Rogan; http://www.bowerbird.org.au/observations/30565) FIGURE 01_6: Silk as Habitat for Metamorphoses. Cocoon of the Bombyx Mori Moth. (Source: https://en.wikipedia.org/wiki/Ahimsa_silk#/media/ File:Cut-cocoon.jpg) FIGURE 01_7: Silk for Predation. Spider Web. (Source: http://photohome.com/photos/animal-pictures/wildlife/spider-web-1.html) FIGURE 01_8: Silk for Habitation. Caterpillar Nest. (Source: https://australianmuseum.net.au/uploads/images/1910/sem10a.jpg) FIGURE 01_9: Spider Silk Glands Under Microscope. (Source: https://australianmuseum.net.au/uploads/images/1910/sem10a.jpg) FIGURE 01_10: Leaf Rolling Caterpillar. Process of Rolling. (Source: https://www.youtube.com/watch?v=4YoKaR9AMhc) FIGURE 01_11: Leaf Rolling Weevil. Finished Nest. (Source: http://sinobug.tumblr.com/post/79746138582/leaf-rolling-weevil-paratrachelophorus-sp) FIGURE 01_12: Weaver Ant and Nest. (Source: http://www.mnn.com/your-home/organic-farming-gardening/blogs/just-add-ants-safer-cheaper-pestcontrol) FIGURE 01_13: Leaf Rolling Caterpillar Habitat. (Source: http://www.bladmineerders.nl/minersf/lepidopteramin/caloptilia/hemidactylella/hemidactylella. htm) FIGURE 01_14: Leaf Rolling of Oak Leaf. (Source: http://www.bladmineerders.nl/minersf/lepidopteramin/caloptilia/hemidactylella/hemidactylella.htm) FIGURE 01_15 - 01_16: Leaf Rolling Process. (Source: https://www.youtube.com/watch?v=4YoKaR9AMhc) FIGURE 01_17: Different Types of Weevil Cutting. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li) FIGURE 01_18 - 01_21: Leaf Rolling Caterpillar. Process or Rolling. (Source: https://www.youtube.com/watch?v=x5641C8yC_0) FIGURE 01_22: Complete Process of Habitat Making. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li; based on Cradles of Attelabidae in Korea

by J.Park J.Lee and J.Park, 2012) FIGURE 01_23: Weaver Ant Nest Building Process. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li; based on Berthold K. Holldobler and Edward O. Wilson, 1977) FIGURE 01_24 - 01_26: Building Process. Weaving, Pulling and Aggregating. (Source: photograph by Mark W. Moffett; http://ngm.nationalgeographic. com/2011/05/weaver-ants/moffett-photography#/01-ant-holding-larva-714.jpg) FIGURE 02_1: Weaver Ant Properties of Construction. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li) FIGURE 02_2 - 02_3: Ant Aggregation for Leaf Pulling and Protection of Queen. (Source: photograph by Mark W. Moffett; http://ngm.nationalgeographic.com/2011/05/weaver-ants/moffett-photography) FIGURE 02_4: Weaver Ants Reaching Across Space. (Source: http://www.antsremoval.com/8-interesting-facts-about-ants/ ) FIGURE 02_5: Weaver Ant Bridge Across Space. (Source: photograph by Adhi Prayoga; http://www.telegraph.co.uk/news/picturegalleries/ earth/10760394/Animal-photos-of-the-week.html?frame=2875761) FIGURE 02_6: Ants Traveling Across Challenging Surfaces. (Source: https://www.shutterstock.com/video/clip-8826019-stock-footage-red-weaver-antworking.html?src=rel/12279449:3/gg) FIGURE 02_7 - 02_9: Weaver Ant Gripping Mechanism: Arolium and Lifting Force. (Source: Thomas Endlein; https://arthropoda.wordpress. com/2010/02/22/weaver-ants-get-a-grip/) FIGURE 02_10: Weaving Process. (Source: image by Norton; http://discovermagazine.com/2008/nov/12-wilson-says-ants-live-in-humanlike-civilizations) FIGURE 02_11: Weaver Ant Carrying Its Larva. (Source: photograph by Jamie Mitchell; https://www.zsl.org/blogs/bugs-blog/profile-jamie-mitchellinsect-keeper) FIGURE 02_12: Weaver Ant Weaving. (Source: photograph by Alex Wild; http://www.antzzz.org/fourmis.php?fourmis=fourmis-fourmiliere&fourmiliere= arboricole) FIGURE 02_13: Weaver Ant Hierarchical Structure of Tasks. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li; based on Peter J.B. Slater, Jay S. Rosenblatt, Charles T. Snowdon, Timothy J. Roper, Marc Naguibah, 2005) FIGURE 02_14: Weaver Ant Hierarchical Sizes. (Source: https://www.antstore.net/shop/en/ants/Ants-from-Asia/Oecophylla-smaragdina-weaver-ants. html) FIGURE 02_15: Weaver Ant Sizes. (Source: J.B. Slater, J. S. Rosenblatt, Charles T. Snowdon, T. J. Roper, M. Naguibah, 2005) FIGURE 02_16: Weaver Ant Nest Building Types. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li) FIGURE 02_17: Weaver Ant Single Leaf Nest Building Types. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li) FIGURE 02_18: Weaver Ant Two Leaf and Unusual Nest Building Types. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li) FIGURE 02_19: Weaver Ant Larger Nest Building Type - Rare Case. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li) FIGURE 02_20 - 02_21: Weaver Ant Nest Types. (Source: photography by Alex Wilde; http://www.alexanderwild.com/) FIGURE 02_22: Weaver Ant Larger Nest Type. (Source: http://thedaysofthepast.blogspot.co.uk/2016/04/warriors-persevere-till-we-see-sunrise.html) FIGURE 02_23: Weaver Ant Nest With an Opening. (Source: photograph by Raghu Mohan; http://www.mnn.com/your-home/organic-farming-gardening/blogs/just-add-ants-safer-cheaper-pest-control) FIGURE 03_1: Weaver Ant Building Process. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li) FIGURE 03_2 - 03_3: Use of Artificial Nests by Weaver Ants. (Source: O. Joachim, 2014) FIGURE 03_4: Experiment Setup Container. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li) FIGURE 03_5 - 03_8: Observations: Relocation of Queen, Feeding, and Weaving. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li) FIGURE 03_9 - 03_13: Weaver Ant Nest Building Process. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li) FIGURE 03_14 - 03_15: Ant Aggregation for Defence During Move to New Habitat. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li) FIGURE 03_16 - 03_17: Ant Aggregation Around Queen During Relocation. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li) FIGURE 03_18 - 03_19: Weaver Ant Nest. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li) FIGURE 04_1: Pulling Chain Formation. (Source: Thomas B. Simon K. A. Robson. Physical and Biological Determinants of Collective Behavioural Dynamics in Complex Systems: Pulling Chain Formation in the Nest-Weaving Ant Oecophylla smaragdina. 2014) FIGURE 04_2: Pulling Formation for Leaf Bending. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li) FIGURE 04_3: Analysis of the Building Process. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li) FIGURE 04_4: Sequence of Adding Leaves to Ant Structures. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li) FIGURE 04_5: Pulling Process in Weaver Ant Building Sequence. (Source: Rasha Alshami, Sabīne Vecvagare, Xun Li) FIGURE 04_6: Physical Models Exploring the Actuation Concept. (Source: Xun Li)

47

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FIGURE 00_1: Weaver Ants (Source: Rasha Alshami, SabÄŤne Vecvagare, Xun Li)