182 INSECTS. 



victim, others deposit more than a hundred. Some 

 undergo their change within its pupa case, while others 

 desert the dying caterpillar, which in this case undergoes 

 no metamorphosis. 



An idea may be formed of the minute size of some of 

 the species, if the student will examine the first twig 

 of a rose-tree that he can find. On this he will see what 

 at first appear to be dead Aphides, brown, hard and stiff, 

 but retaining their perfect form, and, in reality, consist- 

 ing but of empty skins. In each of these he will observe 

 a small round hole, and out of this hole he may know 

 that a little Ichneumon Fly has emerged having been 

 born and brought up within the body of the Aphis. It 

 is said that a Chalcis is parasitic upon this parasite. 

 Bonnet (quoted in " Insect Transformations") tells of a 

 " prodigious number " of some of these parasites being 

 hatched from 20 butterflies eggs. 



It is a curious fact that many insects appear con- 

 scious that the Ichneumon Fly is their natural enemy, 

 show fear at her approach, and endeavour to elude her 

 attacks. 



The fourth family consists of the Chalcis and its re- 

 lations (see PI. VI., fig. 5, C. flavipes). These are mostly 

 very minute parasites of beautiful metallic lustre and 

 colouring. Their wings have but few veins ; in the 

 minutest species none at all. They do not differ greatly 

 from the former family in their habits, but exhibit some, 

 peculiarities of structure. The most conspicuous of 

 these is that in many species the hind legs are of an 

 extraordinary form, the femur or thigh being enormously 

 thickened and sometimes toothed, while the unusual 

 appearance is increased in some species by a great length 

 in the coxa3 of the hind legs. 



