CLASS INSECTS. 



447 



form of a bill or beak, in the interior of which are sharp 

 stylets, adapted to perforate animal or vegetable tissues, in 

 which the animal finds the liquids by which it is nourished 



Fig. 475. Peacock Butterfly (Vanessa io). 



, like all the 



( 523). These insects have generally four wings, like a 

 preceding, but usually those of the first pair are only : 

 branous towards the extremity, and constitute semi-elytra. 



Fig. 476. Danais Plexippa ; a species of Butterfly. 



Finally, the metamorphoses are incomplete, and the insect as 

 it grows changes neither its form nor its habits ; only it in 

 general acquires wings, which it had not at first ; sometimes, 



