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.— Pelecinuspolyturator^ 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. 763 .—chrysis 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 
