342 



ENTOMOLOGY 



302), though essentially a May fly of gigantic proportions (spreading 

 probably 135 mm.), has an odonate type of reticulation; while Xenoneura 

 (Fig. 303) combines characters which are now distributed among Ephe- 

 meridae, Sialidae, Rhaphidiidae, Coniopterygidae, and other families, 

 besides being in many respects unique. These Devonian forms attained 

 huge dimensions -as compared with their recent representatives; Gere- 

 phemera, for example, had an estimated expanse of 175 millimeters. 



FIG. 302. Plalephemera antiqua, natural size. After SCUDDER. 



FIG. 303. Xenoneura antiquorum, five times natural size. After SCUDDER. 



Carboniferous. The Carboniferous age, with its luxuriant vegeta- 

 tion, is marked by the appearance of insects in great number and variety, 

 still restricted, however, to the more generalized orders. The domi- 

 nance of cockroaches in the Carboniferous is especially noteworthy, no 

 fewer than 200 Palaeozoic species being known from Europe and North 

 America. These ancient roaches (Fig. 304) differed from their modern 

 descendants in the similarity of the two pairs of wings, which were alike 

 in form, size, transparency and general neuration, with six principal 

 nervures in each wing; while in recent cockroaches the front wings have 

 become tegmina, with certain of the veins always blended together, 

 though the hind wings have retained their primitive characteristics with 

 a few modifications, such as the expansion of the anal area. Carboni- 

 ferous cockroaches furthermore exhibit ovipositors, straight, slender, 

 and half as long again as the abdomen organs which do not exist in 

 recent species. 



