128 must have been seven inches in expanse of wings. The habits of the modern May-flies show us how animals of this group, living as larvæ in the streams and lakes, must have afforded large supplies of food to fishes, and when mature must have emerged from the waters in countless myriads, filling the air for the brief term of their existence in the perfect state. The May-flies represent another insect order.[50] The Coal-measures of Saarbruck have afforded several species allied to the white ants (_Termites_), insects which must have found abundant scope for their activity in the dead trees of the carboniferous forests. The occurrence of beetles,[51] especially of the weevil family, which have as yet been found only in Europe, might have been expected, considering the habits and modern distribution of this group. It has been asserted that moths[52] have been found in the Carboniferous; but the proof of this, so far as known to me, is the occurrence of leaves, noticed by Sternberg, with markings similar to those made by the larvæ of minute leaf-mining moths. This, however, is uncertain evidence. If we consider the orders of insects not found in the Coal-formation, we can perceive good reasons for the absence of some of them. Those containing the lice and fleas, and other minute and parasitic insects, we can scarcely expect to find. The bees and wasps, and the butterflies and moths, are little likely to have been present where there were scarcely any flowering plants; but such groups as those of the two-winged flies, the plant-bugs and the ants, we might have expected, but for the fact of their being highly specialised forms, and for that reason likely to have appeared later.[53] There are, indeed, as yet no haustellate or suctorial insects known in this early period. Plausible theories of the phylogeny of insects are not wanting; but they do not well suit the known facts as to their first appearance; and perhaps we may venture without much blame to apply to the insects of the Coal-period the remark made by Wollaston with reference to the rich insect fauna of the isolated rock of St. Helena: “To a mind which, like my own, can accept the doctrine of creative acts as not necessarily ‘unphilosophical,’ the mysteries [of the existence of these species in an island so remote from other lands], however great, become at least conceivable; but those which are not able to do this may, perhaps, succeed in elaborating some special theory of their own, which, even if it does not satisfy all the requirements of the problem, may at least prove convincing to themselves.” [Illustration: FIG. 127.—Wings of Cockroaches. From the Coal-formation. _a_, _Archimulacris Acadicus_ (Scudder). _b_, _Blattina Bretonensis_ (Scudder). _c_, _B. Hesri_ (Scudder).] [Illustration: FIG. 128.—Wing of May-fly (_Haplophlebium Barnesii_, Scudder). From the Coal-formation.] [Illustration: FIG. 129.—A Jurassic Sphinx-moth (_Sphinx Snelleri_, Weyenburgh).]