632 



THE STUDY OF INSECTS. 



only about twice the length of the head and thorax. This 

 sex is very rare ; it can be recognized by the venation of 

 the wings, which is similar to that of the female. Nothing 



Fig. 762. — Pelecinus poiyturator, female. 



is known regarding the habits of this species, but it is sup- 

 posed to be parasitic, like the Ichneumon-flies. 



Family CHRYSIDID^E (Chry-sid'i-dae). 



The Cuckoo-flies. 



The cuckoo-flies are wonderfully beautiful creatures, be- 

 ing usually a brilliant metallic green in color. The species 

 are of moderate size, the largest being only about a half 

 inch in length. They can be distinguished from other 

 Hymenoptera by the form of the ab- 

 domen, in which there are only three 

 or four visible segments (Fig. 763), 

 except in the male of a single genus 

 {Cleptes), where there are five. The 

 abdomen is convex above and flat or 

 fig. fo.-chrys/s nitiduia. concave below, so that it can be read- 

 ily turned under the thorax and closely applied to it. In 

 this way a cuckoo-fly rolls itself into a ball when attacked, 

 leaving only its wings exposed. 



Although these insects are handsome, they have very 

 ugly morals, resembling those of the bird whose name has 

 been applied to them. A cuckoo-fly seeks until it finds one 

 of the digger-wasps, or a solitary true wasp, or a solitary 



