Bombus as well as in Apathus, much more variable in color than the females. In Anthrophora retusa the male is of a rich fulvous-brown, while the female is quite black; so are the females of several species of Xylocopa, the males being bright yellow. On the other hand, the females of some species, as of Andræna fulva, are much brighter-colored than the males. Such differences in color can hardly be accounted for by the males being defenceless and thus requiring protection, while the females are well defended by their stings. H. Müller," who has particularly attended to the habits of bees, attributes these differences in color in chief part to sexual selection. That bees have a keen perception of color is certain. He says that the males search eagerly and fight for the possession of the females; and he accounts through such contests for the mandibles of the males being in certain species larger than those of the females. In some cases the males are far more numerous than the females, either early in the season, or at all times and places, or locally; whereas the females in other cases are apparently in excess. In some species the more beautiful males appear to have been selected by the females, and in others the more beautiful females by the males. Consequently, in certain genera (Müller, p. 42), the males of the several species differ much in appearance, while the females are almost indistinguishable; in other genera the reverse occurs. H. Müller believes (p. 82) that the colors gained by one sex through sexual selection have often been transferred in a variable degree to the other sex, just as the pollen-collecting apparatus of the females has often been transferred to the male, to whom it is absolutely useless." * “Anwendung der Darwin'schen Lehre auf Bienen," "Verh. p. n. Jahrg.," xxix. 61 M. Perrier in his article, "La Sélection sexuelle d'aprés Darwin" (“Revue Scientifique," Feb. 1873, p. 868), without apparently having reflected much on the subject, objects that as the males of social bees are known to be produced from unfertilized ova, they could not transmit new characters to their male offspring. This is an extraordinary objection. A female bee fertilized by a male, which presented some character facilitating the union of the sexes, or rendered him more attractive to the female, would lay eggs which would produce only Mutilla Europaea makes a stridulating noise; and according to Goureau" both sexes have this power. He attributes the sound to the friction of the third and preceding abdominal segments, and I find that these surfaces are marked with very fine concentric ridges; but so is the projecting thoracic collar, into which the head articulates, and this collar, when scratched with the point of a needle, emits the proper sound. It is rather surprising that both sexes should have the power of stridulating, as the male is winged and the female wingless. It is notorious that Bees express certain emotions, as of anger, by the tone of their humming; and, according to H. Müller (p. 80), the males of some species make a peculiar singing noise while pursuing the females. Order, Coleoptera (Beetles).-Many beetles are colored so as to resemble the surfaces which they habitually frequent, and they thus escape detection by their enemies. Other species, for instance, diamond-beetles, are ornamented with splendid colors, which are often arranged in stripes, spots, crosses, and other elegant patterns. Such colors can hardly serve directly as a protection, except in the case of certain flower-feeding species; but they may serve as a warning or means of recognition, on the same principle as the phosphorescence of the glow-worm. As with beetles the colors of the two sexes are generally alike, we have no evidence that they have been gained through sexual selection; but this is at least possible, for they may have been developed in one sex and then transferred to the other; and this view is even in some degree probable in those groups which possess other well-marked secondary sexual characters. Blind females; but these young females would next year produce males; and will it be pretended that such males would not inherit the characters of their male grandfathers? To take a case with ordinary animals as nearly parallel as possible; if a female of any white quadruped or bird were crossed by a male of a black breed, and the male and female offspring were paired together, will it be pretended that the grandchildren would not inherit a tendency to blackness from their male grandfather? The acquirement of new characters by the sterile worker-bees is a much more difficult case, but I have endeavored to show in my "Origin of Species" how these sterile beings are subjected to the power of natural selection. 62 Quoted by Westwood, "Modern Class. of Insects," vol. ii. p. 214. Descent-VOL I.-17. beetles, which cannot, of course, behold each other's beauty, never, as I hear from Mr. Waterhouse, Jr., exhibit bright colors, though they often have polished coats; but the explanation of their obscurity may be that they generally inhabit caves and other obscure stations. Some Longicorns, especially certain Prionidæ, offer an exception to the rule that the sexes of beetles do not differ FIG. 16.-Chalcosoma atlas. Upper figure, male (reduced); lower figure, in color. Most of these insects are large and splendidly colored. The males in the genus Pyrodes," which I saw in Mr. Bates's collection, are generally redder but rather 63 Pyrodes pulcherrimus, in which the sexes differ conspicuously, has been described by Mr. Bates in "Transact. Ent. Soc.," 1869, p. 50. I will specify the few other cases in which I have heard of a difference in color between the sexes of beetles. Kirby and Spence ("Introduct. to Entomology," vol. iii. p. 301) mention a Cantharis, Meloe, Rhagium, and the Leptura testacea; the male of the latter being testaceous, with a black thorax, and the female of a dull red all over. These two latter beetles belong to the family of Longicorns. Messrs. R. Trimen and Waterhouse, Jr., inform me of two Lamellicorns, viz., a Peritrichia and Trichius, the male of the latter being more obscurely colored than the female. In Tillus elongatus the male is black, and the female always, as it is believed, of a dark-blue color, with a red thorax. The male, also, of Orsodacna atra, as I hear from Mr. Walsh, is black, the female (the so-called 0. ruficollis) having a rufous thorax. duller than the females, the latter being colored of a more or less splendid golden green. On the other hand, in one species the male is golden green, the female being richly tinted with red and purple. In the genus Esmeralda the sexes differ so greatly in color that they have been ranked as distinct species; in one species both are of a beautiful shining green, but the male has a red thorax. On the whole, as far as I could judge, the females of those Prionidæ in which the sexes differ are colored more richly than the males, and this does not accord with the common rule in regard to color, when acquired through sexual selection. A most remarkable distinction between the sexes of many beetles is presented by the great horns which rise from the head, thorax, and clypeus of the males; and in some few cases from the under surface of the body. These horns, in the great family of the Lamellicorns, resemble those of various quadrupeds, such as stags, rhinoceroses, etc., and are wonderful both from their size and diversified shapes. Instead of describing them, I have given figures of the males and females of some of the more remarkable forms (Figs. 16 to 20). The females generally exhibit rudiments of the horns in the form of small knobs or ridges; but some are destitute of even the slightest rudiment. On the other hand, the horns are nearly as well developed in the female as in the male of Phanaeus lancifer, and only a little less well developed in the females of some other species of this genus and of Copris. I am informed by Mr. Bates that the horns do not differ in any manner corresponding with the more important characteristic differences between the several subdivisions of the family; thus within the same section of the genus Onthophagus there are species which have a single horn, and others which have two. In almost all cases the horns are remarkable from their excessive variability; so that a graduated series can be formed from the most highly developed males to others so degenerate that they can barely be distinguished from |