AFFINITIES OF THE NEXJROPTERA. 337 



space will not permit us to state those reasons which 

 make us decline to view these five groups as orders, 

 a rank to which many excellent entomologists have 

 elevated them. The system of representation, of itself, 

 totally forbids this : the contents of the class Ptilota 

 must agree with those of the Aptera, and both must 

 have their definite number of prototypes in the classes 

 of the vertebrate animals. 



(298.) The affinities by which the order is united 

 into a circle of its own, may be thus briefly stated. The 

 LibellulidcR comprise, beside the sub -family of that 

 name, the Mymeleonince, the Panorpina, the Termince, 

 and the genus Mantispa; which latter appears to be 

 only a representation of the Maritime . We leave these 

 families for the Gryllidce ; of which the genera Mantis, 

 Gryllus, Locusta, Acridium, and Blatta, form the 

 types of the sub-families, and represent those in the 

 LibellulidcB. The crickets seem to open a passage to 

 the ForJiculidcB, which, with the Stylopidce, contain so 

 few genera, that we shall not venture to designate their 

 rank. Finally come the Phryganidce, the leading divi- 

 sions or sub-families of which are the genera Ephemera, 

 Phryganea, Hemerobius, Perla, and Psocus. Each of 

 these correspond analogically, and in precisely the same 

 order, with the primary types, already enumerated, of 

 the Libellulidce and the Gryllida. We look upon these 

 latter as the typical and sub-typical groups ; and the 

 other three as aberrant. A brief notice on the principal 

 genera, in each of these, is all that our limited space 

 will now admit of. 



(299) The large group of insects, here treated col- 

 lectively as Neuropiera, present considerable differences 

 in their structure, transformations, and economy; indeed, 

 so much so, that modern systematists have concurred in 

 treating several of the subdivisions, of which they are 

 here constituted, as distinct orders. Without reference 

 to these views, we shall give some few particulars of their 

 natural history in the order of succession above laid 

 down ; and, in consequence of the difficulty of finding 



