On Synthetic Types in Insects. 591 



a third removed : or again, we see analogous forms be- 

 tween the two higher groups, leaving the lowest for awhile 

 isolated ; or on the otlier hand the two lower groups are 

 thus united, leaving the highest one standing by itself. 

 For example, the clear-winged Sesia imitates the humble- 

 bee in its form and flight ; the different species of ^ge- 

 rians simulate members of nearly every hymenopterous 

 family, as we can see when recalling such names as 

 apiformis, vespiformis, philatithiformis, tiphiaformis, scolice- 

 formis, spheciformis, chrysidiformis, cynipidiformis, formi- 

 ciformis, ichneumonifonnis, uroceriformis, and tenthredini- 

 formis. So also other ^gerians resemble different family 

 forms of Diptera, as seen in the names culiciformis, tipu- 

 liformis, bibioformis, antkraciformis, miAScceformis, &c. In 

 the Diptera we find jBom^/y/iw^, resembling, as its name im- 

 plies, Bombus ; and also Laphria, which so closely apes 

 the humble-bee in its form, coloration, size, and flight, 

 even to the buzz, which is, if anything, still louder. Also 

 there is the strongest resemblance in some Syrphi to Vcspa, 

 and especially to different species of Crabro. But while 

 the Lepidoptera and Diptera resemble the Hymenoptera, 

 we cannot say that Hymenoptera ever assume the form 

 of any flies and moths. They seem isolated ; and re- 

 semble only themselves. In the case of the Laphria, the 

 plump, bee-like form, and the dense yellow and black hir- 

 suties, which cause them to be mistaken for humble-bees by 

 persons unacquainted with their structural differences, are 

 just those features that are exceptional in the Diptera, 

 and are normal in the Hymenoptera. The fly to get them 

 has to pass over one sub-order to obtain a bizarre form 

 which is a prevalent and common family attribute of the 

 Apidffi. 



There is a similar parallelism of analogous forms be- 

 tween the Coleoptera, Hemiptera, Orthoptera, and Neurop- 

 tera, which seem bound together by affuiities such as those 



