Page:Encyclopædia Britannica, Ninth Edition, v. 24.djvu/418

Rh 392 summer, those authorities who put the number of the members of the community as high as 30,000 are probably not far wrong. At the approach of autumn the society begins to break up ; the males fertilize the females whilst flying high in the air. They then die, often within a few hours. The workers leave the nest, carrying with them any grubs that remain in the cells, and both soon perish. The nest is entirely deserted. The females which have been fertilized creep into crevices under stones or trees, or hide amongst moss, and hibernate until the warmth of the following spring induces them to leave their hiding-places and set about founding a new community. There are altogether seven species of Vcspa met with in Britain. V. vulgaris, the common or ground wasp, V. rufa, the red wasp, distinguished by its reddish- yellow legs, and V. gcrmanica, the German wasp, with three black spots upon its first abdo minal segment, are classed to gether as ground wasps. They build their nests in burrows in the ground, but this is not an invariable rule ; they may be distinguished from the tree wasps by the first joint in the antennae of the female being black. The FlG - l Vef P a rt f a - tree wasps build stouter nests upon branches of trees; the first joint of the antennae of the females is yellow in front. The tree wasps are V. arborea, sylvcstris, norwegica, and crabro. The hornet, V. crabro, is the largest species occurring in Great Britain. They have a more distinctly red colour than the common wasp, and a row of red spots upon each side of the abdomen. They occur much more rarely than the common wasp, and appear to be almost confined to the southern half of England. Their nests resemble those described above, but are larger ; they are found in hollow trees or deserted out houses. Their com munities are smaller in number than those of wasps. The hornet, where it occurs in any number, does a con siderable amount of damage to forest trees, by gnawing the bark off the younger branches to obtain material for constructingitsnest. It usually selects the Fl0 2 -- Nest of Vespa sylvestrts - ash or alder, but sometimes attacks the lime, birch, and willow. Like the wasp, it does much damage to fruit, upon the juices of which it lives. On the other hand, the wasp is useful by keeping down the numbers of flies and other insects. It catches these in large numbers, killing them with its jaws and not with its sting. It then tears off the legs and wings, and bears the body back to its nest as food for the larvae. Wasps also act to some extent as flower fertilizers, but in this respect they cannot compare with bees ; they visit fewer flowers, and have no adaptations on their limbs for carrying off the pollen. 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. magnified of the East Indies and Nepal, measure 2 inches across the wings; V. oricntalis, found in Greece, Egypt, and the East, builds its nest of clay. The only other genus of Vespidx which is found in Europe is Polistcs, which occurs in the countries bordering the Mediterranean. The colonies of this genus are much smaller than those of Vcspa. 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 from which it is gathered. The members of this genus have a slender body ; the thorax is more oblong than in the genus Vespa, the palps stouter, and the abdomen more distinctly peduncu late. The genus Ischnognstcr, from the East FIG. 3. Polistes tepidus and nest. Indies, has many structural features in common with the Eumenidss, 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. Synoeca is a South-American genus, which builds large nests, sometimes 3 feet in length, closely applied to the branch of a tree ; they never contain more than one layer of cells, which are horizon tally 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, Chartcrgus, makes a tough nest, pendant 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 pendant, 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 Nectariiia, found in Brazil and other parts of South America, resembles that of the common wasp, but is rougher. Internally the combs are arranged concentri cally, more or less parallel with the external covering which affords them support. The members of the two remaining families, ihefiumenidee and the Masaridx, resemble one another in their solitary mode of life ; only males and females exist, no workers or neuters being found. Family II. Eumenidsz. Solitary species, with three submarginal cells in the fore wing ; antennae with thirteen joints in the male, twelve in the female ; abdomen some times pedunculate, posterior segments contractile. In the foregoing structural features the Eumenidx resemble the Vespidss, but they differ in having bifid claws on their tarsi, and the four anterior tibiae have but one spine at the tip. The mandibles are elongated, and form a kind of rostrum, in this respect approaching the Fossores. Enmenes coarciata is the only British species of this genus. The female is half an inch long, the male somewhat shorter. The abdomen is connected with the thorax by a long peduncle. The colour is black, 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 larva of some species are carnivorous, and then the food supply stored up in the cell con sists 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 Eumencs emerges from the egg it sets upon 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 Eumencs in having a sessile abdomen. Some of the species construct their cells in FIG. 4. Eumenes smilhii.