The Millepedes, like the Land-snails, were first found in the Coal-formation of Nova Scotia, but species have since been discovered not only in Illinois, but also in Great Britain and in Bohemia. In Nova Scotia alone two genera and five distinct species have been found, all in the interior of erect trees, to which these creatures probably resorted for food and shelter ([Fig. 126]). All the species yet known are allied to the modern Gallyworms, though presenting special features which seem to separate them as a distinct family,[46] and were probably vegetable-feeders. Some of the species have the peculiarity, unknown among their modern successors, of being armed with long spines.[47] The moist, equable climate and exuberant vegetation of the Coal-period would naturally be very favourable to Millepedes, and it is likely that the discoveries made as yet give but a faint idea of their actual abundance. It is not improbable that they subsequently declined, as we know of none between the Carboniferous and the Jurassic, and they do not seem to have improved up to the modern period. The Carnivorous Myriapods, however, or Centipedes proper, a higher and essentially distinct type, are not known until much more recent times.
Fig. 126.—Millepedes. From the Coal-formation.
a, Xylobius sigillariæ (Dawson). b, Archiulus xylobioides (Scudder). Anterior segments. Enlarged, c, X. farctus (Scudder). Caudal portion. Enlarged.
The insects of the Carboniferous as yet known, belong to three out of the ten or more orders into which the class is divided. One of these is represented by a number of species of Cockroach, another by May-flies and a Dragon-fly, and another by some weevil-like Beetles. The Cockroach is characterised by Huxley as one of the “oldest, least modified, and in many ways most instructive forms of insects;” and both he and Rolleston take its anatomy as typical of that of the class. That these creatures should have abounded in the Coal-period we need not wonder, when we consider the habits of those that infest our houses, and when we further bear in mind the number of species, some of them two inches in length, that exist in tropical climates. So many species of this family have been found in the Coal-formation on both sides of the Atlantic,[48] that we may fairly regard them as constituting one of its most characteristic features, and as probably the oldest representatives of the order to which they belong[49] ([Fig. 127]). There were also in the Coal-period insects allied to the Locusts and to the Mantids, a carnivorous group. One of the latter (Lithomantis), described by Woodward, is a magnificent insect, not unlike some modern tropical species. It was found in the Coal-formation of Scotland. A still larger species, probably the largest insect known, has been described by Brongniart. The May-flies (Ephemeridæ) are represented in the Carboniferous by several very large species. That of which the wing is shown in [Fig. 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.”
Fig. 127.—Wings of Cockroaches. From the Coal-formation.
a, Archimulacris Acadicus (Scudder). b, Blattina Bretonensis (Scudder). c, B. Hesri (Scudder).