BE EX, WASPS, ANTS, ETC. 



515 



Probably the most common of our large ichneumon-flies arc those of the genus 

 Op/don. The species of this genus are honey yellow in color. At night they are fre- 

 quent ly attracted by light. Ophion macrurum infests the American silkworm, Tdea 

 polyphetnus. The female Ophion lays a single egg in the body of the caterpillar. 

 The caterpillar lives until after it has become full grown and spun its cocoon. It then 



FIG. 644. a, Exenterus marginatorius ; b, Bassus albosignatus. 



perishes before changing to a pupa. The ichneumon larva leaves the body of its host 



and spins a dense cocoon of brownish silk within its cocoon. The shrivelled remains 



of the caterpillar occupies a small space between the two cocoons. 



This same silkworm is infested by another ichneumon-fly, Cryptus extrematis. 



This is a much smaller species, and the female of it, in 



ovipositing, lays many eggs within a single caterpillar. 



The subsequent history of the species is similar to that 



of Ophion. Each Cryptus larva spins a cocoon within 



the cocoon of the silkworm. This results in the latter 



cocoon being packed full of the smaller cocoon. From 



a single Polyphemus cocoon I have bred thirty-five adult 



specimens of Cryptus. 



Two of the smaller European forms are represented 

 in Fig. 644 : Exenterus marginato- 

 rius ovipositing in a caterpillar, and 

 Bassus albosignatus approaching a 

 Syrfrfius larva. Banchus falcator 

 is another common European form. 



The family EVANIID^E is a small 



group comprising insects of very peculiar structure. They are, 

 however, sometimes classed as a sub-family of the Ichneumon ida?. 

 They may be distinguished by the following characters : the an- 

 tennae are filiform or setaceous with not more than sixteen seg- 

 ments, usually with but thirteen or fourteen. The abdomen is 



FIG. 646. Bnncims fai- jointed to the dorsuiii of the metathorax by a peduncle which 



sometimes arises close to the scutellum. The ovipositor is straight 



and often prominent. The fore wings are furnished with a distinct radial cell and 



from one to three cubital cells. The hind wings are almost without veins. The 



FIG. 645. Cryptus extrematis. 



