54 THE CLASS OF INSECTS. 



able manner, those of other groups. They are called mimetic 

 forms. Insects are related to each other by analogy and affin- 

 ity. Thus the truly tailless species of Papilio, i. e. those where 

 the tail is absent in both sexes, are related by affinity to Pie- 

 ris, which has rounded hind wings. They also stand next to 

 Pieris in the system of Nature. But there are, on the other 

 hand, mimetic forms, which borrow the features of groups far 

 above them in the natural system. Thus the Sesia resembles a 

 Bee, Bombylius and Laphria resemble Bomb us ; the Syrphus 

 flies are easily mistaken for Wasps. So in the second series 

 of suborders of Insects, Forjicula resembles the Staphylinus; 

 Termes resembles the true Ant ; Psocus, the AjMs; Ascalaphus 

 resembles Papilio ; Mantispa recalls the Orthopterous Mantis^ and 

 Panorpa reminds us of the Tipulce (Bittacus being strikingly 

 analogous to the Dipterous Bittacomorpha) . Thus these lower, 

 more variable groups of insects strive, as it were, to connect 

 themselves by certain analogous, mimetic forms, with the more 

 stable and higher groups. 



Comprehensive types are mimetic forms which combine the, 

 characters of other and generally higher groups. Thus each 

 Neuropterous family contains mimetic forms which ally them 

 strongly with some one of the six other suborders of insects. 

 The early fossil insects are remarkable for combining the char- 

 acters of groups which appear ages after. The most remark- 

 able comprehensive type is a Carboniferous insect, the Eugereon 

 Boeckingi mentioned farther on. 



Hybriditv. Hybrids are sometimes produced between differ- 

 ent species, but though it is known that different genera unite 

 sexually, we know of very few authentic instances of the pro- 

 duction of hybrids therefrom. One is related by Mr. Midford, 

 who exhibited at the March 4th (1861) meeting of the London 

 Entomological Society, hybrids produced from a male Phiga- 

 lia pilosaria, and a female Nyssia hispidaria. " The males 

 resemble N. Iiispidaria, but in color have the lighter and 

 greener tint and transparency of wing of P. pilosaria." 



The Development of Insects. Immediately after the fer- 

 tilization of the egg, the first act in the organization of the 



