[395] 'Transact. Linn. Soc.' vol. xxv. p. 37.

[396] 'Proc. Entomolog. Soc.' Feb. 17th, 1868.

[397] Quoted by Dr. Wallace in 'Proc. Ent. Soc.' 3rd series, vol. v. 1867, p. 487.

[398] Blanchard, 'Metamorphoses, Murs des Insectes,' 1868, p.

225-226.

[399] 'Lepidopteren-Doubblettren Liste,' Berlin, No. x. 1866.

[400] This naturalist has been so kind as to send me some results from former years, in which the females seemed to preponderate; but so many of the figures were estimates, that I found it impossible to tabulate them.

[401] Gunther's 'Record of Zoological Literature,' 1867, p.

260. On the excess of female Luca.n.u.s, ibid. p. 250. On the males of Luca.n.u.s in England, Westwood, 'Modern Cla.s.s. of Insects,' vol. i. p. 187. On the Siagonium, ibid. p. 172.

[402] Walsh, in 'The American Entomologist,' vol. i. 1869, p.

103. F. Smith, 'Record of Zoological Literature,' 1867, p. 328.

[403] 'Farm Insects,' p. 45-46.

[404] 'Observations on N. American Neuroptera,' by H. Hagen and B. D. Walsh, 'Proc. Ent. Soc. Philadelphia,' Oct. 1863, p. 168, 223, 239.

[405] 'Proc. Ent. Soc. London,' Feb. 17, 1868.

[406] Another great authority in this cla.s.s, Prof. Th.o.r.ell of Upsala ('On European Spiders,' 1869-70, part i. p. 205) speaks as if female spiders were generally commoner than the males.

[407] See, on this subject, Mr. Pickard-Cambridge, as quoted in 'Quarterly Journal of Science,' 1868, p. 429.

[408] I have often been struck with the fact, that in several species of Primula the seeds in the capsules which contained only a few were very much larger than the numerous seeds in the more productive capsules.

[409] 'Principles of Biology,' vol. ii. 1867, chaps. ii.-xi.

[410] 'De l'Espece et de la Cla.s.s.' &c., 1869, p. 106.

[411] See, for instance, the account which I have given in my 'Journal of Researches,' 1845, p. 7.

[412] I have given ('Geolog. Observations on Volcanic Islands,'

1844, p. 53) a curious instance of the influence of light on the colours of a frondescent incrustation, deposited by the surf on the coast-rocks of Ascension, and formed by the solution of triturated sea-sh.e.l.ls.

[413] 'Facts and Arguments for Darwin,' English translat. 1869, p. 20. See the previous discussion on the olfactory threads.

Sars has described a somewhat a.n.a.logous case (as quoted in 'Nature,' 1870, p. 455) in a Norwegian crustacean, the _Pontoporeia affinis_.

[414] See Sir J. Lubbock in 'Annals. and Mag. of Nat. Hist.'

vol. xi. 1853, pl. i. and x.; and vol. xii. (1853) pl. vii. See also Lubbock in 'Transact. Ent. Soc.' vol. iv. new series, 1856-1858, p. 8. With respect to the zigzagged antennae mentioned below, see Fritz Muller, 'Facts and Arguments for Darwin' 1869, p. 40, foot-note.

[415] See a paper by Mr. C. Spence Bate, with figures, in 'Proc. Zoolog. Soc.' 1868, p. 363; and on the nomenclature of the genus, ibid. p. 585. I am greatly indebted to Mr. Spence Bate for nearly all the above statements with respect to the chelae of the higher crustaceans.

[416] 'Hist. Nat. des Crust.' tom. ii. 1837, p. 50.

[417] Fritz Muller, 'Facts and Arguments for Darwin,' 1869, p.

25-28.

[418] 'Travels in the Interior of Brazil,' 1846, p. 111. I have given, in my 'Journal of Researches,' p. 463, an account of the habits of the Birgos.

[419] Mr. Ch. Fraser, in 'Proc. Zoolog. Soc.' 1869, p. 3. I am indebted to Mr. Bate for the statement from Dr. Power.

[420] Claus, 'Die freilebenden Copepoden,' 1863, s. 35.

[421] 'Facts and Arguments,' &c., p. 79.

[422] 'A History of the Spiders of Great Britain,' 1861-64. For the following facts, see p. 102, 77, 88.

[423] Aug. Vinson ('Araneides des Iles de la Reunion,' pl. vi.

figs. 1 and 2) gives a good instance of the small size of the male in _Epeira nigra_. In this species, as I may add, the male is testaceous and the female black with legs banded with red.

Other even more striking cases of inequality in size between the s.e.xes have been recorded ('Quarterly Journal of Science,'

1868, July, p. 429); but I have not seen the original accounts.

[424] Kirby and Spence, 'Introduction to Entomology,' vol. i.

1818, p. 280.

[425] Theridion (Asagena, Sund.) serratipes, 4-punctatum et guttatum; see Westring, in Kroyer, 'Naturhist. Tidskrift,' vol.

iv. 1842-1843, p. 349; and vol. ii. 1846-1849, p. 342. See, also, for other species, 'Araneae Svecicae,' p. 184.

[426] Walckenaer et P. Gervais, 'Hist. Nat. des Insectes: Apteres,' tom. iv. 1847, p. 17, 19, 68.

[427] Sir J. Lubbock, 'Transact. Linnean Soc.' vol. xxv. 1866, p. 484. With respect to the Mutillidae see Westwood, 'Modern Cla.s.s. of Insects,' vol. ii. p. 213.

[428] These organs in the male often differ in closely-allied species, and afford excellent specific characters. But their importance, under a functional point of view, as Mr. E.

MacLachlan has remarked to me, has probably been overrated. It has been suggested, that slight differences in these organs would suffice to prevent the intercrossing of well-marked varieties or incipient species, and would thus aid in their development. That this can hardly be the case, we may infer from the many recorded cases (see for instance, Bronn, 'Geschichte der Natur,' B. ii. 1843, s. 164; and Westwood, 'Transact. Ent. Soc.' vol. iii. 1842, p. 195) of distinct species having been observed in union. Mr. MacLachlan informs me (vide 'Stett. Ent. Zeitung,' 1867, s. 155) that when several species of Phryganidae, which present strongly-p.r.o.nounced differences of this kind, were confined together by Dr. Aug.

Meyer, _they coupled_, and one pair produced fertile ova.

[429] 'The Practical Entomologist,' Philadelphia, vol. ii. May, 1867, p. 88.

[430] Mr. Walsh, ibid. p. 107.

[431] 'Modern Cla.s.sification of Insects,' vol. ii. 1840, p.

206, 205. Mr. Walsh, who called my attention to this double use of the jaws, says that he has repeatedly observed this fact.

[432] We have here a curious and inexplicable case of dimorphism, for some of the females of four European species of Dytiscus, and of certain species of Hydroporus, have their elytra smooth; and no intermediate gradations between sulcated or punctured and quite smooth elytra have been observed. See Dr. H. Schaum, as quoted in the 'Zoologist,' vol. v.-vi.

1847-48, p. 1896. Also Kirby and Spence, 'Introduction to Entomology,' vol. iii. 1826, p. 305.

[433] Westwood, 'Modern Cla.s.s.' vol. ii. p. 193. The following statement about Penthe, and others in inverted commas, are taken from Mr. Walsh, 'Practical Entomologist,' Philadelphia, vol. ii. p. 88.

[434] Kirby and Spence, 'Introduct.' &c., vol. iii. p. 332-336.

[435] 'Insecta Maderensia,' 1854, p. 20.

[436] E. Doubleday, 'Annals and Mag. of Nat. Hist.' vol. i.

1848, p. 379. I may add that the wings in certain Hymenoptera (see Shuckard, 'Fossorial Hymenop.' 1837, p. 39-43) differ in neuration according to s.e.x.