METAMORPHOSIS OF INSECTS. 355 
sponding to those of the butterfly), and four ot five pairs of 
unjointed clasping abdominal “ pro-legs.” Other abdominal 
appendages are known on the larve of other insects, and 
even in the embryos of some whose larve are campodei- 
form. These facts make it likely that the primitive form 
had many legs. 
The larvee of Insects vary enormously in habit and in structure, and 
exhibit numerous adaptations to conditions of life very different from 
‘hose of the parent. Thus caterpillars, which are usually plump and 
Fic. 187.—Development of blow-fly (Calliphora 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; %., the large hooks connected 
with the maxille ; J/., pro-legs. 
The upper figure (B) shows the pronymph removed from the pupa- 
case. In the abdominal region the imaginal discs are shown ; 
2., rudiments of legs; w., 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 larve develop gradually into those of the 
adult. But in Insects with complete metamorphosis there 
