96 Mr. A. S. Packard on the Development 



the Hemiptera are numerous aquatic species, as there are in all 

 the other suborders except the Hymenoptera, of which only two 

 genera are found swimming, in the adult state, on the surface of 

 pools; and they are the low minute Proctotrupids, Prestwichia 

 natans and Polynema nutans, Lubbock. As we have previously 

 shown, the Hymenoptera do not imitate or mimic the forms of 

 other insects, but, on the contrary, their forms are extensively 

 copied, in the Lepidoptera and Diptera especially. There are 

 synthetic types or mimetic forms which bind these suborders 

 into a single series. As the Coleoptera, Hemiptera, Orthoptera, 

 and Neuroptera are bound together by homomorphous or mi- 

 metic forms into a series by themselves, so the Hymenoptera, 

 Lepidoptera, and Diptera possess their synthetic types linking 

 them together. 



Another and very accurate method of determining the relative 

 rank of the larger groups in nature is by comparing the degra- 

 dational forms occurring in each group. Among the Neuroptera 

 the lowest wingless forms, such as Lepisma and allies, most 

 strikingly resemble the Myriapods in the great equahty in size 

 of the arthromeres composing the body, and the slight dis- 

 tinctions preserved between the three regions into which the 

 body is divided. The largest, most vegetative, monstrous, and 

 bizarre forms of insects are found among the Neuroptera and 

 Orthoptera. Among Hemiptera the parasitic wingless lice, and 

 among Coleoptera the low Meloe and Stylopidse, afford instances 

 of a genuine complete parasitism such as obtains more fully 

 among the low Crustacea and worms. While we find the de- 

 graded types of Insects belonging to the lower series of sub- 

 orders present elongated, worm-like, myriapodous forms,in ascend- 

 ing to the second and higher series of suborders, the lowest wing- 

 less dipterous Pulex assumes a much compacter, more cephalized 

 form ;; while in the wingless Chionea, which wonderfully mimics 

 the higher Arachnids, there is a still greater concentration of 

 the arthromeres. This concentration of the body progresses 

 towards a higher type in the degradational forms of the Lepido- 

 ptera, such as the wingless females of Orgyia, Amsopteryx, and 

 Hybernia. In ascending to the wingless Hymenoptera, such as 

 Pezomachus, Formica, and Mutilla, there is a closer approxima- 

 tion to the winged normal form of the suborder. While in the 

 lower Insects the loss of wings involves apparently a total change 

 in the form of the body, in the Hymenoptera this change is re- 

 markably less than in any other insects, and the tripartite form 

 of the insectean body is more strongly adhered to. 



Again, in the degradational winged forms of the Hymenoptera 

 we find the antennge rarely pectinated — a common occurrence in 

 the lower suborders ; also the wings of the minute Proctotru- 



