Page:EB1911 - Volume 28.djvu/377

Rh The genus Vespa is very widely spread; it contains over forty species, distributed all over the world. Some of the largest and handsomest come from eastern Asia. V. mandarina of China and Japan, and V. magnifica of the East Indies and Nepal, measure . 2.—Nest of Vespa sylvestris. 2 in. across the wings; V. orientalis, found in Greece, Egypt and the East, builds its nest of clay.

The only other genus of Vespidae which is found in Europe is Polistes, which occurs in the countries bordering the Mediterranean. The colonies of this genus are much smaller than those of Vespa. Each nest consists of a single tier of cells in the form of a round plate, supported in the middle by a single stalk. This comb is sometimes vertical, the cells then being horizontal or slightly oblique. Some of the members of this genus store up honey, which in the case of a South American species is poisonous, from the nature of the flowers The members of this genus have a slender body; the thorax is more oblong than in the genus Vespa, the palps are stouter and the abdomen is more distinctly pedunculate.

The genus Ischnogaster, from the East Indies, has many structural features in common with the Eumenidae, but the character of its communities, and its nest, which is very small, justify its position amongst the social wasps.

The genus Icaria, common in Australia and the East Indies, builds very small nests, of two or three rows of cells, hanging on one side from a stalk.

Synaeca is a South American genus, which builds large nests, sometimes 3 ft. in length, closely applied to the branch of a tree; they never contain more than one layer of cells, which are horizontally placed. The whole nest is built of coarse material, chiefly small pieces of bark; and there is only one opening, at the lower end.



Another South American genus, Chartergus, makes a tough nest, pendent from boughs of trees, and opening to the exterior below by a median aperture. The combs are arranged, somewhat like funnels, inside one another, but with spaces between. The apex of each comb is pierced by a hole for the wasps to pass from one gallery to another.

The nest of Tatua, which occurs in Mexico and South America, is also pendent, but the combs are horizontal; the opening from the exterior is at the side, and the passage from one gallery to another is also lateral.

The external appearance of the nest of Nectarina, found in Brazil and other parts of South America, resembles that of the common wasp, but is rougher. Internally the combs are arranged concentrically, more or less parallel with the external covering which affords them support.

The members of the two remaining families, the Eumenidae and the Masaridae, resemble one another in their solitary mode of life; only males and normal females, exist—no workers being found.

Family 2. Eumenidae.—Solitary species, with three submarginal cells in the fore wing; antennae with thirteen joints in the male, twelve in the female; abdomen sometimes pedunculate, posterior segments contractile. In the foregoing structural features the Eumenidae resemble the Vespidae, but they differ in having bifid

claws on their tarsi, and the two anterior tibiae have but one spine at the tin. The mandibles are elongated, and form a kind of rostrum, in this respect approaching the Fossores.

Eumenes coarctata is the only British species of this genus. The female is &frac12; in. long, the male somewhat shorter. The abdomen is connected with the thorax by a long peduncle. The colour is black, . 4. Eumenes smithii. relieved by spots of yellow. It constructs small spherical cells of mud, which are found attached to stems of plants, very generally to the heath. At first the cell opens to the exterior by means of a round pore; one egg is deposited in each cell, and a store of honey as food for the larva when hatched; the cell is then closed with mud. The larvae of some species are carnivorous, and then the food-supply stored up in the cell consists of caterpillars and other insect larvae which have been paralysed by the parent wasp stinging them through the cerebral ganglion; when the larva of the Eumenes emerges from the egg it sets up these and devours them.

The genus Odynerus contains a very large number of species, found in all parts of the world. The members of this genus are about the size of a fly, and they differ from Eumenes in having a sessile abdomen. Some of the species construct their cells in sand-heaps, lining them with agglutinated grains of sand; others live in cavities of trees lined with the same material, whilst others build their nests of mud. Like some of the species of Eumenes, they store up paralysed Lepidopterous and Chrysomeleous larvae as food for their carnivorous grubs.

Family 3. Masaridae.—The members of the third family, the Masaridae, are sharply distinguished by the possession of only two submarginal cells in the fore wing, which folds imperfectly or not at all when at rest. Their antennae are frequently clavate, particularly so in the genus Celonites; they are twelve-jointed, but as the terminal joints are almost fused they appear to be composed of only eight joints. The wings are not so completely folded as in the other two families, and the abdomen is but slightly contractile. The maxillae are short and their palps very small, with but three or four joints.

The number of genera comprised in this family is small; none occur in Britain, but in southern Europe some species are found. They make their nest in cavities in the earth, generally in a bank and construct an irregular gallery leading down to it.

During hot fine summers wasps cause a good deal of loss to market gardeners and fruit growers. During this time of year they live almost exclusively upon the sweet juices of ripe fruit, occasionally carrying off small particles of the flesh. At the same time they have not entirely lost their carnivorous tastes, for they frequently attack the meat in butcher's shops, but render compensation by killing and carrying off to feed their grubs considerable numbers of blow-flies. Wasps also perform an important service in keeping down the numbers of caterpillars. The larvae are almost exclusively carnivorous, living . 5.—Masaris vespiformis. upon insects captured by their parents and reduced by them to a pulp before being given to the young. During the spring the first broods that appear live largely upon honey; and this forms the staple food of the genus Polistes throughout their whole life.

In attempting to rid a district of wasps, unless the nest can be taken, there is little good in killing stray members of the community. On the other hand, the killing of queen-wasps in early spring probably means that the formation of a nest and the production of a society whose members are counted by thousands is in each case prevented.

The number of wasps is kept down by numerous enemies. The most effective of these live in the nests and devour the larvae; among them are two species of beetle, Rhipiphorus paradoxus and Lebia linearis. Two species of Ichneumon, and a species of Anthomyia, also infest the nests of wasps and prey upon the grubs. The larvae of the syrphid flies Volucella, found in the nests of both wasps and bees, are now believed to be scavengers rather than parasites. In the tropics some species are attacked by fungi, the hyphae of which protrude between