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 

 itiduia. 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 



