INTUOnUCTION. 13 



Haustellata. But different authors are not agreed as to the 

 sequence in which they place the Orders of Insects. 



Of all the principal Orders, the Order Neuroptera is in the most 

 unsatisfactory state, including a great number of very discordant 

 groups, which difter extremely in the structure of their mouths and 

 in the character of their metamorphoses. It has even been pro- 

 posed to unite the bulk of the Netiropfem with the Orthoptera, under 

 the improper title of Pseudo-Neuroptera, leaving only a very few 

 (scarcely typical) groups to represent the Neuroptera. But the 

 Neuroptera which most resemble the Orthoptera, differ from them 

 so widely in the structure of their wings that even Linn6 did not 

 place them in the same Order ; and it would be a mistake to do so 

 at the present day. 



No system can, however, be regarded as perfect. Organic 

 Nature is now believed to have grown up into the form in which Ave 

 see it from infinitesimal beginnings, by the effect of gradual changes 

 actins: and reactins; on each other in the course of countless ages. 

 AVe have consequently nothing before us to classify but the extreme 

 ends of the branches of a vast tree, of the rest of which we are 

 scarcely able to catch even the slightest glimpse. Consequently, 

 Avhile every group and every species is more or less related to 

 others, a book-arrangement can only be linear, and while it 

 expresses a certain amount of affinity between the groups and 

 species placed in juxtaposition, it likewise tends to conceal the fact 

 that equally important affinities frequently exist between other 

 species or groups, Avhich may chance to be widely separated in our 

 necessarily artificial arrangements. 



Of fossil insects but little need here be said. Comparatively 

 few species have yet been described, for the correct identification 

 of the fragmentary remains of insects which are sometimes met 

 with (occasionally in considerable abundance) presents difficulties 

 Avhich are almost insuperable to the best entomologists, Avho are 

 not always agreed respecting even the Order to which an insect 

 belongs; while in other cases, fragments originally supposed to 

 belong to insects have ultimately proved to be of vegetable origin. 

 Sometimes, hoAvever, fossil insects are met Avith in such good 

 preservation that but little difficulty exists in determining their 

 approximate affinities. The oldest knoAvn fossil insects appear to 

 belong to the Orders Orthoptera and Neuroptera, and some of the 

 latter Avere of gigantic size compared to their nearest living allies. 

 Even such fragile insects as butterflies are occasionally met Avith in 



