570 METAMORPHOSIS OF INSECTS. 



some Insects (such, as the Grasshopper and the Cricket) which 

 come-forth from the egg in a form so nearly resembling that 

 which they are ultimately to present, that the deficiency of 

 wings is their principal difference. Such are said to undergo 

 an incomplete metamorphosis; the fact being, however, not 

 that these finally attain a less elevated condition than other 

 Insects, but that they make a much nearer approach to it in 

 that part of their embryonic state which they pass within the 

 egg. In the tribes of Beetles, Butterflies, Bees, and Flies, on 

 the other hand, the embryo comes-forth from the egg in the 

 condition of a Worm ; and only acquires either the form or 

 structure of an Insect after a complete metamorphosis, in which 

 every part of its organization undergoes important modifica- 

 tions. The larva, sometimes known as a " maggot," sometimes 

 as a " caterpillar " or " grub," is in many instances completely 

 destitute of legs ; and where it does possess feet by which it 

 can crawl, these are not jointed members, but mere fleshy 

 protuberances. The segments are all nearly equal and similar, 

 both externally and internally; they are never more than 

 thirteen in number, counting the head as one and having 

 been all formed in the first instance by the subdivision of the 

 original yolk-mass, they undergo no subsequent augmentation 

 but that of size. The voracity of the larva is its most extra- 

 ordinary characteristic ; and its increase in bulk is propor- 

 tional, the full-sized larva being estimated in some instances 

 to weigh no less than 72,000 times as much as it did when it 

 came-forth from the egg (141). During this rapid increase, its 

 skin is several times thrown off; a new one being first formed 

 within, this, better adapted to its augmented size. Very little 

 change takes place in the structure of the larva, until after 

 the completion of its growth ; it then ceases to eat, and fre- 

 quently forms some protection to itself, either by spinning a 

 silken cocoon, or by gluing bits of stick, straw, &c. into a 

 case, or it may bury itself in the ground. The last larva-skin 

 hardens into a firm case around the body, which, diminishing 

 in size, shrinks away from its interior. The creature, now 

 known as a chrysalis or pupa, remains for some time without 

 food and apparently inert ; important changes, however, are 

 taking place within its body, which tend towards the forma- 

 tion of the organs of the perfect insect ; and these are pro- 

 duced at the expense of the mass of nutrient material that 



