HYMENOPTERA. 



23 



black, with reddish legs, the wings being better furnished with nervures than in other 

 members of the family. In the chrysalis-stinger (Pteromalus puparum) the egg 

 is laid in the chrysalis of several common butterflies during summer, while the 

 larvae remain in their host all through the winter, sometimes to the number of fifty. 



1 3 2 



I, gouty-legged wasp ; 2, chrysalis-stinger ; 3, Sketches of various Chalcididce (enlarged). 



The Ichneumon-Wasps, — Family Ichneumonibje. 



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

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

 of Lepidoptera, 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 

 variation of the wings, though these characters 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 deposits an egg with Jier 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 miarginatorius) figured in the 

 illustration on p. 24, which belongs to the subfamily Tryphonince, and is 

 found chiefly in pine-woods, where it is parasitic on Lophyrus pini, described on 

 p. 16. 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 gradually absorbs. The perfect insect makes a small hole in the 

 pupa-case when it emerges, and does not, as does L. pini, bite off a little cap at 

 the top. Another type is Bassus albosignatus, which frequents the honey-dew 

 dropped by aphid colonies. It lays its eggs on various larvae which feed upon the 



