INTRODUCTION, 



21 



or incompletely in all insects. Their metamorphoses are then at an 

 end. There are certain insects, however, that show no difference in 

 their various stages, except by absence of wings in the larva ; and in 

 these the chrysalis is only characterised by the growth of the wings, 

 which, at first folded back and hidden under the skin, afterwards 

 become free, but are not wholly developed till the last skin is cast. 

 These insects are said to undergo incomplete metamorphoses, the 



Fig. 16. Hydrophilus in its four states. 

 A, eggs ; B, larva ; C, pupa ; D, imago, or perfect insect. 



former complete metamorphoses. Some never possess wings ; indeed, 

 there are others which undergo no metamorphosis, and are born pos- 

 sessed of all the organs with which it is necessary they should be 

 provided. 



Some curious researches have been lately made on the strength of 

 insects. M. Felix Plateau, of Brussels, has published some observations 

 on this point, which we think of sufficient interest to reproduce here. 



