INTRODUCTION. 



2! 



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

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

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

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

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

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

 rhese insects are said to undergo incomplete metamorphoses, the 



Fig. i6. — 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. 



Certain curious researches have been made on the strength of in- 

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

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



