54 THE CLASS OF INSECTS. 



able manner, those of other gi'oujDS. 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 gi'oups far 

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

 Bee, Bomhylius and Lapliria resemble Bomhus; the Syrphus 

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

 of suborders of Insects, Forjicula resembles the Skqjhyliuus ; 

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

 resembles Pcqnlio ; Mantispa recalls the Orthopterous Mantis, and 

 Panorpa reminds us of the TipulcB {Bittacus being strikinglj^ 

 analogous to the Dipterous Bittabomorpha) . 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. 



Comjyrehensive 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 tyi^e is a Carboniferous insect, the Eugereon 

 Boeckingi mentioned farther on. 



Hybridity. Hybrids are sometimes produced between differ- 

 ent species, but though it is known that diflerent 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, Itybrids produced from a male Pliiga- 

 lia p)iiosaria, and a female J^yssia Jiisjndaria. "The males 

 resemble I^. Jiisjyidaria, but in color have the lighter and 

 greener tint and transparency of wing of P. pilosaria" 



The Development op Insects. Immediately after the fer- 

 tilization of the egg, the fii'st act in the organization of the 



