1 88 TRANSFORMATIOl^S OF INSECTS. 



office of the parasitic Hymenoptera becomes most evident, and they 

 evidently render us most important services, for they check the 

 ravages of the larvae which destroy cereals, vines, and vegetables 

 of all kinds. The balance of life between the vegetables, the 

 caterpillars, and the parasites is most extraordinary. A few cater- 

 pillars come from the ^^g of one butterfly, perhaps in a newly 

 cultivated district, and they are not noticed. The next year hun- 

 dreds of caterpillars are found devouring everything, and then 

 one or two stray Ichneumons come upon the scene. They are so 

 clever that they never miss their aim, and they lay thousands of 

 eggs in as many caterpillars. The year following there are fewer 

 caterpillars, and a great host of Ichneummu, that riddle every 

 insect that comes in their way. Spring comes round again, and 

 there are no caterpillars, vegetation flourishes, and then comes the 

 turn of the parasites. Their office is completed, and they pass 

 away. It is thus that armies of caterpillars suddenly appear and 

 disappear. 



There is some difficulty in applying the word parasite to all 

 insects that live in intimate relation with others. The parasite just 

 noticed lives at the expense of the vital juices of its victim or host. 

 It does not devour the body, and then remain glutted. But many 

 insects, like human parasites, only eat the provisions which others 

 have laid up in store for the rainy day, or for their ofl*spring, and 

 these, of course, should be called the true parasites. Others live 

 with their strange companions, and look out for scraps, and what 

 happens to come in their way, these are comrades, and are very 

 common in many families of the Artimlata. 



The IchnenmonidcB have, as a rule, long thin bodies, slender 

 legs, very large wings, which are much veined, and long, slender, 

 vibrating, thread-shaped antennae. Agility is written in every 

 structure of the Ichneumons ; the jaws have long palps; and the 

 slender body, large wings, and the legs, which can be used for run- 

 ning, indicate unusual locomotive powers. The lively appearance 

 of the insects is heightened by their projecting eyes and the long 

 and restless antennae. They are not to be caught readily, but 

 rush off" with wonderful rapidity out of the way of danger, and 

 if a female is seized she endeavours to stick her ovipositor into 

 the fingers of her captor. 



