1422 THE STORY OF THE UNIVERSE 



orders, it is not, I think, conceivable that the latter 

 should have been derived from any known species of 

 the former; on the other hand, the earliest known 

 Neuroptera and Orthoptera, though in some respects 

 less specialized than existing forms, are as truly and 

 as well characterized insects as any now existing; 

 nor are we acquainted with any earlier forms which 

 in any way tend to bridge over the gap between them 

 and lower groups, though, as we shall see, there are 

 types yet existing which throw much light on the 

 subject. 



The stag-beetle, the dragon-fly, the moth, the 

 bee, the ant, the gnat, the grasshopper these and 

 other less familiar types seem at first to have little 

 in common. They differ in size, in form, in color, 

 in habits, and modes of life. Yet the researches of 

 entomologists, following the clew supplied by the 

 illustrious Savigny, have proved not only that while 

 differing greatly in details they are constructed on 

 one common plan, but also that other groups, as, 

 for instance, Crustacea (lobsters, crabs, etc.) and 

 Arachnida (spiders and mites), can be shown to be 

 fundamentally similar. 



Thus, then, although it can be demonstrated that 

 perfect insects, however much they differ in appear- 

 ance, are yet reducible to one type, the fact becomes 

 much more evident if we compare the larvs. M. 

 Brauer and I have pointed out that two types of 

 larvae, which I have proposed to call Campodea- 

 form and Lindia-form, and which Packard has 

 named Leptiform and Eruciform, run through the 

 principal groups of insects. 



