i8o ECONOMIC ZOOLOGY AND ENTOMOLOGY 



females of certain wasps. In many Hymenoptera the front 

 margin of the hind wings bears a series of small recurved hooks 

 which, when the wings are outspread, fit over a ridge on the 

 hind margin of the fore wing thus fastening the two wings firmly 

 together. The mouth-parts are variously modified, but usu- 

 ally are fitted for both biting and lapping. This is arranged for 

 by having the maxillae and labium more or less elongated and 

 forming a sort of proboscis for taking up liquids, while the 

 mandibles always retain their short, strong, j aw-like character. 

 The females throughout the order are provided either with a 

 saw-like or boring or pricking egg-layer (ovipositor), or with 

 the same parts modified to be a sting. 



In the development of all Hymenoptera the metamorphosis 

 is complete, and the larvae are, more than in any other order, 

 helpless and dependent for their food and safety on the 

 special provision or care of the parents. The parasitic species 

 lay their eggs either on or in the body of the insect which is to 

 serve as food for the larvae, while the gall-making kinds lay 

 their eggs in the plant tissue on which their larvae feed. With 

 most of the solitary wasps and bees, food is stored up in the cell 

 in which the egg is deposited, so that the larvae on hatching will 

 find it ready. With the social wasps and bees and all the ants, 

 the workers bring food to the young during their whole larval 

 life. 



The Hymenoptera may be roughly divided into a few im- 

 portant groups. First, the saw-flies (family Tenthredinidce) 

 whose larvae, soft-bodied, naked, caterpillar-like creatures, 

 usually with six to eight pairs of abdominal legs besides the 

 three pairs of thoracic legs, are called slugs. Common kinds 

 are the current-slug, rose-slug, larch-slug and others, which do 

 considerable damage by eating away the soft tissues leaving 

 only the veins, thus making "skeletons" of the leaves of their 

 food plants. The saw-flies compose a large family, 600 species 

 being known in this country, but the adults are rarely seen by 

 the general observer. 



Second, the great group of parasites comprising several 

 families (Ichneumonidce, BraconidcE, Chalcididce, Proctotrypidce, 

 and others), and including species varying in size from the 



