568 Dr. Thomas Algernon Chapman on the 



cutaneous structure and possessmg no hard chitinous 

 parts, the imaginil append xges ai-e all present, quite dis- 

 tinct and separate from each other^ but incapable of any 

 movement. 



The exceptions in these two orders in which the pupa 

 is exposed, and consequently of harder external texture, 

 are by no means few in actual number, but are isolated 

 to single species, genera, and rarely families, and seem 

 nowhere to have given occasion to any further evolu- 

 tional development. 



Actually numerous as these exceptions maybe, in com- 

 parison with the totals of these large orders, it is hardly 

 erroneous to neglect them, and say that the protected 

 pupa of delicate texture is universal throughout these 

 two orders, and that no further development by 

 departui-e from this rule has taken place within them. 



In all protected pupas the problem has to be faced, how 

 is the imago to free itself from the cocoon or other 

 envelope protecting the pupa. In the Hymcnoptera and 

 CoJeoptera this is effected by aid of the imaginal jaws. 

 The imago becomes perfect within the cocoon ; it not 

 only throvvs off the pupal skin within the cocoon, but 

 remains there till its appendages have become fully 

 expanded and completely hardened, and then the man- 

 dibles are used to force an outlet of escape. Throughout 

 these orders it is the rule that the imago requires its jaws 

 for other purposes — purposes that we may regard as the 

 primary reason for their existence. Still, their use to 

 extricate the insect from its pupal residence can hardly 

 be called a secondary matter, and in many cases, even in 

 pome whole families, they are of no use whatever to the 

 imago except in this one paiticular; the Cynipidx are 

 perhaps the most striking instance of this circum- 

 stance. 



Certain families of the Keuroptera struck out a new 

 line in this matter. One or two families appear to have 

 followed the same lines precisely as the Coleoptera and 

 Hymenoptera. Whether the new departure was a 

 development from these, or whether it was in some way 

 a partial retention of the characteristics of the active pupa, 

 i have no materials to decide ; but the fact is, that in a 

 group of families the pupa, otherwise quiescent and of 

 delicate structure, retained well-developed mandibles, 

 and by aid of these the pupa extricates itself from the 



