2986 



THE JOINTED ANIMALS 



THE ICHNEUMON WASPS Family 



The species included in this vast family number upward of six thousand, and 

 doubtless more remain to be discovered. The majority are parasitic on the larvae 

 of L/epidoptera, rendering good service to the agriculturist and gardener by holding 

 in check the enormous quantities of larvae hatched every year. Some, however, 

 attack other insects as well as spiders. The family is distinguished by the varia- 

 tion of the wings, though these characteristics vary too slightly to be of much value 

 for generic or specific purposes. The antennae are of uniform thickness, many 

 jointed, and, as a rule, filiform, though in some exceptional cases club shaped. 

 The ichneumon wasps do not hum, either when quiescent or on the wing, and are 

 thus enabled to approach the victim within whose body they wish to lay their eggs 

 with a greater chance of success. Having selected a suitable caterpillar, the female 



1. Exenterus marginatorius, about to sting the larva of Lophyrus pini; 2. Pupa case of the latter with the 

 parasite emerged; 3. With the proper sawfly emerged; 4. Bassus albosignatus, about to attack a Syrphus- 

 larva; 6. Banchus falcator; 7. Pupa of the ichneumon. 



(Natural size.) 



deposits an egg with her ovipositor either on or beneath its skin. The egg soon 

 hatches, and the grubs feed upon the tissues of the larvae until full fed, when they 

 pupate in or around the now almost empty skin of the caterpillar. The family has 

 been divided into five groups, sufficiently distinguished from each other in their 

 typical forms, but merging into one another through transitional species. Our first 

 example is the ichneumon (Exenterus marginatorius) figured in the accompanying 

 illustration, which belongs to the subfamily Tryphonince, and is found chiefly in pine 

 woods, where it is parasitic on Lophyrus pini, described on p. 2978. The female 

 attaches an egg by means of a hooklet to the skin of the green larvae, when nearly 

 full grown. When the insect forms its barrel-shaped pupa, in which to pass the 

 winter, the parasite remains attached to the skin of the larva, whose tissues it 



