those employed by the Homoptera." But throughout the animal kingdom we often find the same object gained by the most diversified means; this seems due to the whole organization having undergone multifarious changes in the course of ages, and as part after part varied different variations were taken advantage of for the same general purpose. The diversity of means for producing sound in the three families of the Orthoptera and in the Homoptera impresses the mind with the high importance of these structures to the males, for the sake of calling or alluring the females. We need feel no surprise at the amount of modification which the Orthoptera have undergone in this respect, as we now know, from Dr. Scudder's remarkable discovery," that there has been more than ample time. This naturalist has lately found a fossil insect in the Devonian formation of New Brunswick, which is furnished with "the well-known tympanum or stridulating apparatus of the male Locustidæ.' The insect, though in most respects related to the Neuroptera, appears, as is so often the case with very ancient forms, to connect the two related Orders of the Neuroptera and Orthoptera.

I have but little more to say on the Orthoptera. Some of the species are very pugnacious. When two male fieldcrickets (Gryllus campestris) are confined together, they fight till one kills the other; and the species of Mantis are described as manoeuvring with their sword-like front limbs, like hussars with their sabres. The Chinese keep these insects in little bamboo cages, and match them like gamecocks. 45 With respect to color, some exotic locusts are beautifully ornamented; the posterior wings being marked with red, blue, and black; but as throughout the Order the

43 Landois has recently found in certain Orthoptera rudimentary structures closely similar to the sound-producing organs in the Homoptera; and this is a surprising fact. See "Zeitschr. für Wissensch. Zoolog., B. xxii. Heft. 3, 1871, p. 348.

44 Transact. Ent. Soc.," 3d series, vol. ii. ("Journal of Proceedings,"

p. 117).

45 Westwood, "Modern Class. of Insects," vol. i. p. 427; for crickets, p. 445.

sexes rarely differ much in color, it is not probable that they owe their bright tints to sexual selection. Conspicuous colors may be of use to these insects, by giving notice that they are unpalatable. Thus it has been observed" that a bright-colored Indian locust was invariably rejected when offered to birds and lizards. Some cases, however, are known of sexual differences of color in this Order. The male of an American cricket" is described as being as white as ivory, while the female varies from almost white to greenish-yellow or dusky. Mr. Walsh informs me that the adult male of Spectrum femoratum (one of the Phasmida) "is of a shining brownish-yellow color; the adult female being of a dull, opaque, cinereous brown; the young of both sexes being green.' Lastly, I may mention that the male of one curious kind of cricket" is furnished with "a long membranous appendage, which falls over the face like a veil"; but what its use may be is not known.

Order, Neuroptera.-Little need here be said, except as to color. In the Ephemeride the sexes often differ slightly in their obscure tints;" but it is not probable that the males are thus rendered attractive to the females. The Libellulidæ, or dragon-flies, are ornamented with splendid green, blue, yellow, and vermilion metallic tints; and the sexes often differ. Thus, as Prof. Westwood remarks," the males of some of the Agrionidae "are of a rich blue with black wings, while the females are fine green with colorless wings." But in Agrion Ramburii these colors are exactly reversed in the two sexes. In the extensive North Americans genus of Hetarina, the males alone have a beautiful

51

46 Mr. Ch. Horne, in "Proc. Ent. Soc.," May 3, 1869, p. xii.

47 The Ecanthus nivalis. Harris, "Insects of New England," 1842, p. 124. The two sexes of E. pellucidus of Europe differ, as I hear from Victor Carus, in nearly the same manner.

48 Platyblemnus: Westwood, "Modern Clas.," vol. i. p. 447.

49 B. D. Walsh, the "Pseudo-neuroptera of Illinois," in "Proc. Ent. Soc., of Philadelphia," 1862, p. 362.

50 Modern Class., 66

"vol. ii. p. 37.

51 Walsh, ibid., p. 382. I am indebted to this naturalist for the following facts on Hetærina, Anax, and Gomphus.

carmine spot at the base of each wing. In Anax junius the basal part of the abdomen in the male is a vivid ultramarine blue, and in the female grass-green. In the allied genus Gomphus, on the other hand, and in some other genera, the sexes differ but little in color. In closely allied forms throughout the animal kingdom, similar cases of the sexes differing greatly, or very little, or not at all, are of frequent occurrence. Although there is so wide a difference in color between the sexes of many Libellulidæ, it is often difficult to say which is the more brilliant; and the ordinary coloration of the two sexes is reversed, as we have just seen, in one species of Agrion. It is not probable that their colors in any case have been gained as a protection. Mr. MacLachlan, who has closely attended to this family, writes to me that dragon-flies-the tyrants of the insect-worldare the least liable of any insect to be attacked by birds or other enemies, and he believes that their bright colors serve as a sexual attraction. Certain dragon-flies apparently are attracted by particular colors. Mr. Patterson observed" that the Agrionidæ, of which the males are blue, settled in numbers on the blue float of a fishing line, while two other species were attracted by shining white colors.

It is an interesting fact, first noticed by Schelver, that, in several genera belonging to two sub-families, the males on first emergence from the pupal state are colored exactly like the females; but that their bodies in a short time assume a conspicuous milky-blue tint, owing to the exuda tion of a kind of oil, soluble in ether and alcohol. Mr. MacLachlan believes that in the male of Libellula depressa this change of color does not occur until nearly a fortnight after the metamorphosis, when the sexes are ready to pair.

Certain species of Neurothemis present, according to Brauer," a curious case of dimorphism, some of the females having ordinary wings, while others have them “very richly netted, as in the males of the same species.'

52 Trans. Ent. Soc.," vol. i., 1836, p. lxxxi.

68 See abstract in the "Zoological Record" for 1867, p. 450.

Brauer "explains the phenomenon on Darwinian principles by the supposition that the close netting of the veins is a secondary sexual character in the males, which has been abruptly transferred to some of the females instead of, as generally occurs, to all of them." Mr. MacLachlan informs me of another instance of dimorphism in several species of Agrion, in which some individuals are of an orange color, and these are invariably females. This is probably a case of reversion; for in the true Libellulæ, when the sexes differ in color, the females are orange or yellow; so that, supposing Agrion to be descended from some primordial form which resembled the typical Libellulæ in its sexual characters, it would not be surprising that a tendency to vary in this manner should occur in the females alone.

Although many dragon-flies are large, powerful, and fierce insects, the males have not been observed by Mr. MacLachlan to fight together, excepting, as he believes, in some of the smaller species of Agrion. In another group in this Order, namely, the Termites, or white ants, both sexes at the time of swarming may be seen running about, "the male after the female, sometimes two chasing one female, and contending with great eagerness who shall win the prize. The Atropos pulsatorius is said to make a noise with its jaws, which is answered by other individuals."

Order, Hymenoptera.-That inimitable observer, M. Fabre," in describing the habits of Cerceris, a wasp-like insect, remarks that "fights frequently ensue between the males for the possession of some particular female, who sits an apparently unconcerned beholder of the struggle for supremacy, and, when the victory is decided, quietly flies away in company with the conqueror. Westwood"

54 Kirby and Spence, "Introduct. to Entomology," vol. ii., 1828, p. 35. 55 Houzeau, "Les Facultés Mentales," etc., tom. i. p. 104.

56 See an interesting article, "The Writings of Fabre," in "Nat. Hist. Review," April, 1862, p. 122.

57 See the "Journal of the Proceedings of the Entomological Society" for September 7, 1863, p. 169.

says that the males of one of the saw-flies (Tenthredina) "have been found fighting together, with their mandibles locked." As M. Fabre speaks of the males of Cerceris striving to obtain a particular female, it may be well to bear in mind that insects belonging to this Order have the power of recognizing each other after long intervals of time, and are deeply attached. For instance, Pierre Huber, whose accuracy no one doubts, separated some ants, and when, after an interval of four months, they met others which had formerly belonged to the same community, they recognized and caressed one another with their antennæ. Had they been strangers they would have fought together. Again, when two communities engage in a battle, the ants on the same side sometimes attack each other in the general confusion, but they soon perceive their mistake, and the one ant soothes the other.

68

69

In this Order slight differences in color, according to sex, are common, but conspicuous differences are rare except in the family of Bees; yet both sexes of certain groups are so brilliantly colored-for instance in Chrysis, in which vermilion and metallic greens prevail-that we are tempted to attribute the result to sexual selection. In the Ichneumonidæ, according to Mr. Walsh, the males are almost universally lighter-colored than the females. On the other hand, in the Tenthredinidæ the males are generally darker than the females. In the Siricide the sexes frequently differ; thus the male of Sirex juvencus is banded with orange, while the female is dark purple; but it is difficult to say which sex is the more ornamented. In Tremex columbæ the female is much brighter-colored than the male. I am informed by Mr. F. Smith that the male ants of several species are black, the females being testaceous. In the family of Bees, especially in the solitary species, as I hear from the same entomologist, the sexes often differ in color. The males are generally the brighter, and, in

58 P. Huber, "Recherches sur les Moeurs des Fourmis," 1810, pp. 150, 165. " "Proc. Entomolog. Soc. of Philadelphia," 1866, pp. 238-239.