I METAMORPHOSES OF INSECTS 3 



they differ much, are all more or less in an immature 

 stage. Gradually the larvae alter to the quiescent 

 pupae, the nymphs so-called, and from the pupa 

 emerges the perfect beetle. Bees, wasps, flies, and 

 many more undergo similarly marked metamor- 

 phoses. 



The metamorphoses of some insects, however, 

 are far less decided, as in the grasshoppers, locusts, 

 crickets, earwigs, and a small group well-known 

 to gardeners under the name of thrips. In these 

 the larvae and pupae already greatly resemble the 

 fully-developed parent. The changes consist prin- 

 cipally in a gradual increase of size, with casts of 

 skin, and as pupae the insects begin to show signs 

 of the acquisition of wings. In certain cases the egg- 

 stage is wanting, the larva being produced alive, 

 There are rare anomalies in which development has 

 been carried to a considerable degree before birth. 



The difference in the nature of metamorphoses has 

 given rise to a simple division of insects into two 

 series : Heteromorpha, according to Professor West- 

 wood, or those in which there is no resemblance 

 between the parent and the offspring ; and Homo- 

 morpha, or those in which the larva resembles the 

 imago, except in the absence of wings. In the former 

 the insects may be said to undergo complete meta- 

 morphoses ; as regards the latter, their metamorphoses 

 are incomplete. 



It may be laid down as a universal law that all insects 

 originate from eggs. The apparent exceptions com- 

 prise the few instances where the young are hatched, or 

 are retained within the body of the mother. The varieties 



B 2 



