The Bug Report: Wasps — Predators, Parasitoids, and Pollinators By: Kylie Etter, Ecology Technician
W
asps are wonderful. They are essential contributors to healthy ecosystems. These hard-working critters are in the Order Hymenoptera along with bees (vegetarian wasps), ants (wingless, social wasps), and sawflies (prehistoric wasps). Why am I calling beloved bees “vegetarian wasps”? Well, bees evolved over 100 million years ago from a group of wasps to utilize pollen as their main food source for their offspring. The line between bees and wasps is fuzzy. A good, works-most-of-the-time way to tell bees and wasps apart is that wasps generally have less hair and no hairs forming stripes and, frankly, they just look tougher. Wasps are very diverse, with over 100,000 described species belonging to 89 currently recognized families worldwide. There are likely hundreds of species yet to be described by science. Wasps vary in size, color, and life history. The smallest wasps measure under 0.04 inches (1 millimeter) and the largest are up to 1.57 inches (4 centimeters). Wasps can be metallic or matte, spotted or striped, and a vast array of colors. Wasps are also very diverse in their life histories, ranging from predators (figures 1 and 2) to parasitoids (figures 3, 4, and 5) and social to solitary ground nesters (figures 1 and 2).
Figure 1: Thread-waisted sand wasps (Ammophila sp., Family Sphecidae) provision their nests with caterpillars and sawflies (BugGuide). Sand wasps paralyze their prey and carry the prey back to their nest in their mandibles, seen protruding here. (Photo: Kylie Etter)
20 Ironwood
Parasitoid wasps must have been the inspiration for some of the biggest science-fiction horror movies in history, like the “Alien” franchise. Parasitoid wasps lay their eggs in or on an insect host, where their little ones get all their necessary nutrients until they eventually kill the host and emerge as adults. A pretty spooky but important-to-understand life history! Some parasitoids have a broad group of hosts and are opportunistic, while others parasitize only a single species. Parasitoid wasps are used in biological control (aka, bio-control) for a lot of agricultural fruit and vegetable pests and can be thanked for keeping the plant-munching insects in your own garden in check. If you are not screaming “I love wasps!” yet or even “I guess wasps are important!,” maybe this can sway you: Wasps are pollinators also! A pollinator is any animal that picks up pollen from a flower and deposits it on the stigma of the same or different flower. Some wasps may stop for nectar while doing the hard task of catching and dragging food home for their offspring (figures 1 and 2 were captured on flowers). Other wasps, such as pollen wasps (subfamily Masarinae) have actually abandoned the meat-filled diet for their growing babies, and they provide their young with pollen and nectar like bees do (figure 6).
Figure 2: A sand wasp (Bembix sp., Family Crabronidae) on a California brittlebush (Encelia californica) flower at the Devereux Slough at University of California, Santa Barbara. Sand wasps usually nest in sandy ground and prey on flies to feed their young (Photo: Kylie Etter)
