METAMORPHOSIS OF INSECTS. 



355 



spending to those of the butterfly), and four or five pairs ot 

 unjointed clasping abdominal " pro-legs." Other abdominal 

 appendages are known on the larvae of other insects, and 

 even in the embryos of some whose larvae are campodei- 

 form. These facts make it likely that the primitive form 

 had many legs. 



The larvae of Insects vary enormously in habit and in structure, and 

 exhibit numerous adaptations to conditions of life very different from 

 tfiose of the parent. Thus caterpillars, which are usually plump and 



FlG. 187. Development of blow-fly (Cattiphora erythrocephala\ 

 After Thompson Lowne. 



The lower figure (A) shows the adult larva (maggot). Note, as 

 compared with the caterpillar, the absence of appendages, 

 except those about the mouth; h. y the large hooks connected 

 with the maxillae ; //., pro-legs. 



The upper figure (B) shows the pronymph removed from the pupa- 

 case. In the abdominal region the imaginal discs are shown ; 

 /., rudiments of legs ; /., of wings. 



tense, so that a peck from a bird's bill may cause them to bleed to death, 

 even if no immediate destruction befall them, are protectively adapted 

 in many different ways. Their colours are often changed in harmony 

 with those of their surroundings ; some palatable forms are saved by 

 their superficial resemblance to those which are nauseous ; a few strike 

 " terrifying attitudes" ; while others are like pieces of plants. 



Internal metamorphosis. In Insects with no marked 

 metamorphosis, or with merely an incomplete one, the 

 organs of the larvae develop gradually into those of the 

 adult. But in Insects with complete metamorphosis there 



