504 NATURAL HISTORY OF ARTHROPODS. 



gives the name to the order (umen, membrane ; pteron, wing). The wings are either 

 naked or covered with tine microscopic hairs. They are usually transparent, some- 

 times clouded, and frequently they are iridescent. The veins are comparatively few 

 in number. In special works on Hymenoptera each of the veins of the wing and each 

 of the cells or spaces circumscribed by the veins is given a distinct name. It is not, 

 however, worth while in this place to enumerate these names. 



The front wings are larger than the hind ones. Each front wing has a thickened 

 spot near the lateral extremity of the front margin. This is the stigma, and is repre- 

 sented by the shaded portions in our figures. The two wings of each side are united 

 during flight by a series of minute hooks on the front margin of the hind wings. 

 These hooks catch the hind margin of the front wings, so that the two wings present 

 a continuous surface. 



As in all the other orders of insects we find here species which are destitute of 

 wings ; and there are species in which one sex is wingless and the other winged. 

 While with the ants the males are winged, the sterile females (workers) are wingless ; 

 and the fertile females (queens) have wings at first, but shed them after the occur- 

 rence of the flight, in which the pairing of the se.xos takes place. 



The legs are generally long and slender, with five-jointed tarsi. Various modifi- 

 cations of form will be noted later. The form of the abdomen varies to a remarkable 

 degree. It may be joined to the thorax by a slender pedicel or by nearly its entire 

 width. It may be composed of short and very broad segments, or of long and slender 

 joints. Between these extremes there are all gradations. Figures of the more im- 

 portant modifications will be given in connection with the various families. In the 

 females the caudal end of the body is furnished with a complicated apparatus known 

 sometimes as a sting and sometimes as an ovipositor. In the higher families it is a 

 sting, and is connected with a poison gland. In the lower families it is of many forms. 

 In some species it is a multivalve saw fitted for cutting slits into leaves for the inser- 

 tion of eggs. In others it is a boring instrument by which a deep circular hole can be 

 made in solid wood. Again the different parts of which it is composed merely serve 

 to guide the eggs to the desired place during oviposition. 



In their transformations the Hymenoptera undergo a complete metamorphosis, 

 the form in which they first appear on leaving the egg being very different from that 

 they assume in the adult state. The eggs of the Hymenoptera present little that is 

 remarkable in form or coloring. Usually they are longer than broad, with rounded 

 extremities, and with a thin smooth shell, which is rarely colored. Certain parasitic 

 species fasten their eggs to other insects by means of stalks. In some members of the 

 order the eggs swell before hatching until they are neaiiy or quite twice the size that 

 they were when first laid. The number of eggs laid by a single female varies greatly; 

 with some of the solitary species it is probably not more than ten or twelve, while 

 with the social species it may be more than the same number of thousands. 



In the two lower families the larvaa are furnished with legs, and frequently have a 

 striking resemblance to caterpillars. Like the larvae of Lepidoptera these aberrant 

 forms feed upon leaves or bore into the woody portions of plants. But in the other 

 families the Iarva3 are footless, maggot-like creatures, incapable of any extended 

 motion, and entirely dependent on the instinctive care of the adult insects. To a 

 certain extent this dependence is also true in the case of the lower families, for if the 

 parent saw-fly were not to lay her eggs upon the proper kind of plant the larvae would 

 starve. In the higher and more typical members of the order the care exercised over 



