182 niNTS ON THE ANCESTRY OF INSECTS. 



tiuguished from that of the adult insect almost solely by the want 

 of wings," while tlie freshly hatched young of the bee, we may 

 add, is farthest from the form of the adult. It is evident "that in 

 the young grasslioppers, the metamorphoses have been passed 

 through, so to speak, in the egg, while the bee larva is almost 

 embrj'onic in its build. The helpless young maggot of the 

 wasp, which is fed solely by the parent, may be compared to 

 the human infant, while the lusty young grasshopper, which 

 immediately on hatching takes to the grass or clover field with 

 all the enthusiasm of a duckling to its native pond, may be 

 likened to that young feathered mariner. The lowest animals, 

 as a rule, are at birth most like the adult. So with the earliest 

 known Crustacea. The king crabs, and in all probability the 

 primeval trilobites, passed through their metamorphoses chiefly 

 in the egg. So in the ancient Nebaliads (Peltocaris, Discino- 

 caris and Ceratiocaris), if we may follow the analogy of the 

 recent Nebalia, the young probably closely resembled the adult, 

 while the living crabs and shrimps usually 

 pass through the most marked metamor- 

 phoses. Among the worms, the highest, 

 and perhaps the most recent forms, pass 

 through the most remarkable metamor- 

 phoses. 

 209. Jaws of Aut Liou. , ., i ^ 41 , ^. • i. ,. 



Another puzzle for the evolutionist to 



solve is how to account for the change from the caterpillar 

 with its powerful jaws, to the butterfly with its sucking or 

 haustellate mouth-parts. We shall best approach the solution 

 of this difllcult problem by a study of a wide range of facts, but 

 a few of which can be here noticed. The older entomologists 

 divided insects into haustellate or suctorial, and inandlbulate or 

 biting insects, the butterfly being an example of one, and the 

 beetle serving to illustrate the other category. But we shall 

 find in studying the diflerent groups that these are relative and 

 not absolute terms. We find mandibulate insects with enor- 

 mous jaws, like the Dytiscus, or Chrysopa larva or aut lion, 

 perforated, as In the former, or enclosing, as in the latter two in- 

 sects, the maxillae (Ji), which slide backward and forward within 

 the hollowed mandibles («, Fig. 209, jaws of the ant lion), along 

 which the blood of their victims flows. They suck the blood, and 

 do not tear the flesh of their prey. The enormous mandibles of 

 the adult Corydalus are too large for use and, as Walsh observed, 



