374 ORDERS OF PTILOTA. 



nerves is greatly diminished, and in a few, as the Chalcididae 

 and Proctotrnpidae, the nerves are almost, and even abso- 

 lutely and entirely, obliterated. In many of these insects 

 a remarkable apparatus exists, whereby the two wings on 

 each side are kept steady together in flight, consisting of a 

 series of very minute hooks or crotchets, discoverable under 

 a good magnifier on the anterior margin of the posterior 

 wings. They have been noticed by no other authors than 

 De Geer and Kirby, the latter of whom observes, that they 

 are much more conspicuous in the bees than in the winged 

 ants. The legs, which are six in number, are inserted on 

 the lower side of the thorax, and consist of various pieces, 

 which contribute to their movements. These pieces are the 

 coxa, a short inece connecting the leg with the thorax; 

 trochanter, another short piece articulated between the coxa 

 and the following piece, and which, in the Ichneumonidae, is 

 divided into two parts ; the femur, or thigh, which is long 

 and robust ; the tibia, or shank, which is more slender, and 

 terminated by one or two spurs ; and the articulated tarsus, 

 which constantly consists of five joints, the fifth being of a 

 conical form, the extremity being the thickest part, and 

 furnished with two strong but small claws, between which 

 the pulvilli, or cushions, are often to be observed. These 

 legs, which are, in fact, the chief organs whereby the insects 

 are enabled to carry on their varied economy and habits, are 

 necessarily very varied in their form, and in the appendages 

 wdth which they are furnished. The abdomen, which is also 

 of a very varied form, is attached to the posterior part of the 

 thorax, either by its entire width, in which case it is said to 

 be sessile, or by means of a slender peduncle, or foot-stalk, 

 which in some groups is also as long as the abdomen itself. 

 At the extremity of this abdomen, on its lower surface, is 

 attached the ovipositor, saw, or sting above mentioned, 

 each of which, although varied in form, so as to suit its 



