A Trip to British Guiana

36

A TRIP TO BRITISH

GUIANA.

A TRIP TO BRITISH GUIANA. BY

O. W .

RICHARDS,

M.A.,

D.Sc.,

HON.

SEC.

R.E.S.

IN the summer of 1937 my wife and I visited British Guiana to study insect life there ; we were accompanied by Dr. John Smart of the British Museum, Nat. Hist., another entomologist, and by M r . N. Y. Sandwith of Kew Gardens, who was collecting plants. W e two were principally interested in Bees and Wasps, and gave most attention to the very interesting social kinds that are so numerous there.—The colony of British Guiana lies on the north-west of South America, about eight hundred miles above the equator. T h e country rises in a series of low terraces from the coastal area, which is just below sea-level and protected by seawalls. T h e low coastal strip, only a few miles broad, is cultivated chiefly with sugar and rice ; all the roads excepting one, and the sole railway in the country, are close to the coast. Almost all the rest is covered by timber, with some relatively small areas of savannah on the southern and eastern borders ; and access to the interior is made possible only by the four or five large rivers which come down from the interior ; their navigation is badly interfered with by rapids or waterfalls where the steps from one terrace to another are passed.—The greater part of this large area of 90,000 sq. miles is covered by virgin forest of the same type as the rain-forest of Amazonia, though differing in detail.

Along the rivers and near Settlements, of which none (away from the coast) possesses over a few hundred inhabitants, the aboriginal timber has been felled or burned, and a different type of second-growth forest has replaced i t ; the plants and animals of these parts are frequently species widely spread over tropical America, but in the virgin forest, altered but slightly by removal of timber that is chiefly Greenheart, Oecotea rodicei, Schomb., the species are often much more local and many more of them are peculiar to British Guiana.

Most of our stay was spent at Mazaruni Station, a govt. resthouse about forty miles from the coast, up the great River Essequibo and near the small town of Bartica where the Rivers Cuyuni and Mazaruni join the main Essequibo. This Station is the headquarters of part of the Forestry Dept. and is also the site of a prison. It is surrounded by a Clearing, probably artificial but at least a Century old, which is kept grassy by cutting and burning.

A second-growth forest begins about a half-mile away with a rather sharply defined boundary. This low and much-burned forest grades into relatively untouched timber about two miles from the house ; two or three paths have been cut for some miles, making it possible to explore what otherwise would be almost impenetrable bush. T o study plants or animals such paths must be made if not already existent since, apart from the difficulty of

A TRIP TO BRITISH GUIANA.

37

Walking, one could not attend to biology without getting lost !

Actually it seems that Insects, too, take advantage of the light and space thus afforded, and abound most along them, though this may be a fallacy.—Every traveller in the Tropics, especially South America, has told of the general absence of any showy plants and animals, which at first disappoints him in virgin forest: this is due to more than one cause. Conspicuous Flowers are most commonly seen along river-edges, where the aboreal canopy descends lower and is seen in section : the forest-top would probably present a similar appearance, though everywhere flowers tend to be lost amid the profusion of greenery Many trees have small greenish flowers ; and the large red or yellow masses of blossoming Lianes, Bignoniacece, etc., are not really very numerous and may not flower for very long. Upon the actual floor of the forest are only a few Saprophytes, analogous to our Birds-nest Orchid (Neottia nidus-avis, Rieh.), but of quite different families: these, though sometimes beautiful, are small and inconspicuous.

The larger VERTEBRATES are clearly very much less numerous than in Africa : Jaguar (Felis onca, L.), Peccaries (Dicotyles spp.), Monkeys (Cebidoe), Accouri (Agouti = Dasyprocta spp.) and Labba(Paca = Ccelogenys paca, L.) all occur but are rarely seen by a casual Wanderer. To meet with much of these animals one must go out in early morning, and stand long silently : in a two months' sojourn we did actually see Peccaries, Monkeys and Accouri, one or two Boa-constrictors (Boa constrictor, L.) and Alligators (Caiman scurops, Schneid.) but on most days nothing large would be visible. Among BIRDS, the position is rather similar though they are somewhat less elusive : the vast bulk of bird-fauna consist of small and often drab-coloured species, such as the Ant-birds (Formicariid.ce). The most conspicuous larger kinds are the Cara-Cara (small Vultures,Ibycter spp., Macaws (Ă„ra macao, L.) and Toucans (Ramphastos spp.), while the minute Humming-birds (Trochilidee) are fairly common ; all these can be watched, though they are usually shy and keep to the tops of trees which average about ninety feet. No doubt a trained ornithologist would find much of interest.

Amongst INSECTS, the Ants are probably the most important: although some are large and striking, it is their utter ubiquity and ' nuisance-value ' that attract attention. T h e Leaf-cutting Ants (Atta, and allied genera) are so common as to be a serious menace to cultivation ; their nests are subterranean, consisting of mounds two-four feet high and perhaps ten-twenty feet in diameter that are penetrated by tunnels as large as rat-holes and lead to nest-chambers sometimes twelve feet deep in the earth.

Many such mounds are connected and, apparently, a single nest may be joined by underground passages at least a quarter-mile long. Above ground, workers bring their leaf-fragments along

38

A TRIP TO BRITISH

GUIANA.

well-beaten tracks ; on most days a few are visible but sometimes, when a particular tree has reached the stage they like, dense processions of them walk in each direction until it is completely stripped : the leaves, when chewed, form the material on which fungus is cultivated by these Ants. Innumerable other kinds exist, with most varied habits : two or three hundred species can be found in a quite small area. The Termites are probably just as abundant as individuals, but are much less conspicuous owing to their avoidance of light; nevertheless, almost every piece of rotten wood on the forest floor is riddled with their galleries and, in some places, their large earthen nests are quite common on trees.

I can say little about Butterflies that are abundant and, especially in more open parts, often beautifully coloured, for we studied them very little because they are much better known than other Guiana insects : we collected only Skippers, wanted by the Natural History Museum. Some six hundred kinds of Rhopalocera, I believe, are known in the Colony. Moths are also numerous ; and, probably to a European collector, the great variety of Pyrales, that are often beautifully marked, is the most outstanding feature. Large species in general, and Hawk-moths especially, were not common though some striking ones were captured. Dragonflies are very abundant, many of them beautiful : in the forest, more especially, live the genus Mecistogaster and its allies, which are said to breed in water contained in the leaf-bases of epiphytic plants. These insects have a thin abdomen about four inches in length and long wings, sometimes white-tipped ; they flit about amongst the trees with a deceptively slow flight, and are difficult to capture because their habit is to thread a way among the branches. One small species, yellow and black winged, hovered over a forest-swamp with an extraordinary flight, every wing very rapidly vibrating like those of a Skipper. Bees and Wasps are equally abundant, and many very interesting: the most conspicuous Bees are Meliponids, stingless, allied to our Honey Bee. They build large social nests, often in hollow trees, and vary in size from three mm. long to rather larger than Apis mellifica, L. Species of Euglossa are solitary Bees with extremely long tongues, hoverers over flowers and unusually rapid flyers ; the nests are made of mud or resin in hollow stems or attached to leaves. Those of the genera Centris and Xylocopa are also large and conspicuous.—Amongst Wasps the most striking are numerous social kinds, the majority belonging to the Polybiinoe, a group which is mainly South American : they build paper, or very rarely mud, nests that usually hang from or are attached to trees. Unlike British social Wasps, each nest generally contains many egg-laying females, and queens are little different from workers. Much of our time was spent in studying such Wasps, and my wife dissected some

39

ENGLISH'S INEXACTITUDE.

thousands in order to record the condition of the ovaries: much Variation appears in the number of queens in a nest, of even a single species.

A visit to the Kaietour Fall* was most interesting; it is some hundred and twenty miles inland from us and reached by lorry to Kangaruma, followed by an all-day trip up the River Potaro in a motor-boat. The Falls drop a sheer seven hundred and forty feet at a point where the Potaro is of the breadth of the Thames. A few yards from the falls is a govt. rest-house beside a mile-broad savannah, whereon grow over a score kinds of Bladderwort (Utricularia spp.), mostly in sand. These species, like the great majority of our collections, have not yet been adequately worked through. * T h i s Fall is said to be five times as high as Niagara ; and another has been recently discovered here t h a t is the highest in the world, with a füll half-mile's sheer drop. Guiana is Britain's sole S o u t h American possession and Sir Walter Raleigh's El-Dorado, that n o w both takes and sends us one million p o u n d s ' worth of goods annually.

ENGLISH'S INEXACTITUDE. T o THE HON. EDITOR.

My Dear Sir.—Many thanks for the Index to our Transactions, vol. iii 1935-7, safely received today.—I have been much exercised by a question which, at first sight, seems entirely puerile and yet might puzzle wiser heads than mine : Is a Winkle a ' creature' ?

Apparently certain of our legislators, who sanction the present colossal expenditure upon Education, brought their wits to bear upon this matter and failed to agree. In fact I have just been told that, in a discussion upon the Fishing Industry bill, one M.P. intemperately declared the Winkle to be a Fish ; another maintained that it was an Animal; and a third, determined to be right, pronounced it a Creature. To the best of my belief it is an Amphibian ; for I have seen Winkles left on mud by the receding tide at, say, the first quarter-ebb where the water would not again reach them tili the last quarter-flood, when they would have to endure the sun's rays for some ten hours.

The river Crab, too, walks over mud and makes a hole in the bank, wherein it deposits its old shell and does not leave this casting-place until its new carapace is hard enough to resist enemies' assaults : so I take it that the Crab, also, is an Amphibian.

Most truly yours, Suffolk ; 17th February, 1938.

A MEMBER.

GOVERNMENT

RFST-HOUSE

AT

MAZARUNI.

INDIAN H U T S ON E D G E OF P R I M A R Y

FOREST.