604 TEXT-BOOK OF ENTOMOLOGY 



a structure which would enable it to move about freely after its 

 prey, beginning at once to live a sedentary life in the egg-sac of a 

 spider; before the first moult it loses the use of its legs, while the 

 antennae are partly aborted. The result is that, owing to this 

 change of habits and surroundings from those of its active ancestors, 

 it changes its form, and the fully grown larva becomes cylindrical, 

 with small slender legs, and, owing to the partial disuse of its jaws, 

 acquires a small, round head. 



Its antennae, mouth-parts, and legs not only retarded in growth, 

 but retrograding and becoming vestigial, the body meanwhile 

 becoming fat and cylindrical, an apparent acceleration of growth 

 goes on within, with probably an enlargement of the intestine and 

 fat-body, and thus the pupal form is perfected while the larva is 

 full-fed and quiescent. It is not improbable that in the primitive 

 neuropteron, as the result of a mode of life like that of Mantispa, 

 the quiescent life of the later stages graduated into a quiescent, 

 inactive pupal life, allowing the changes going on in the internal 

 organs to result in a complete metamorphosis, which was transmitted 

 to the later Keuroptera, thus making the complete metamorphosis 

 a fixed, normal condition. It thus appears that a change of habits 

 and of food, and more especially the fact that the nymph became so 

 surrounded with an abundance of food close at hand that it did not 

 have to run actively about and seize it in a haphazard manner, were 

 the factors bringing about a change from the Campodea-form nymph 

 to the eruciform larva, thus inducing a hypermetamorphosis. 



The larvae of the Mecoptera (Panorpidae, Fig. 562, b) are still more 

 caterpillar-like, and besides their cylindrical body, rounded head, 

 small short gnathites, small thoracic legs, they have what appear 

 to be 2-jointed legs to each of the nine abdominal segments, and 

 the close resemblance to caterpillars is farther carried out by the 

 presence of a pair of prothoracic spiracles, none existing on the 

 other two thoracic segments. 



In the Meloidae (Fig. 560, d) and Stylopidae the first larval stage 

 is Campodea-form; the changes will be described in the subse- 

 quent section on Hypermetamorphosis, and while these cases of 

 change from a campodeoid to an inactive eruciform larva are very 

 salient, if we compare the graduated series of larval forms through- 

 out the order of Coleoptera, as represented by the illustrations in 

 Fig. 561, we shall see that in nearly, if not each, case the form of 

 the boring or mining, or bark or bud or seed-inhabiting grub is the 

 result of a change of habit and commissariat from active predaceous 

 larvae, like those of the Carabidae and other adephagous families, 



