286 THE DESGKNT OF MAN, 



So that in these eight lots of cocoons and eggs males were pro- 

 duced in excess. Taken together the proj)ortion of males is as 122.7 

 to 100 feradles. But the numbers are hardly large enough to be 

 trustworthy. 



On the whole, from these various sources of evidence, all pointing 

 in the same direction, I infer that with most species of Lepidopteru 

 the mature males generally exceed the females in number, whatever 

 the proportions may be at their first emergence from the egg. 



With reference to the other orders of insects, I have been able to 

 collect very little reliable information. With the stag-beetle {La- 

 canus cei'viis) " the males appear to be much more numerous than 

 the females:" but when, as Cornelius remarked during 1867, an 

 unusual number of these beetles appeared in one part of Germany, 

 the females appeared to exceed the males as 6 to 1. With one 

 of the Elateridae, the males are said to be much more numerous than 

 the females, and "two or three are often found united with one 

 female;* so that here polyandry seems to prevail." With Siagonium 

 (Staphylinidae), in which the males are furnished with horns, ' ' the 

 females are far more numerous than the opposite sex." Mr. Janson 

 stated at the Entomological Society that the females of the bark- 

 feeding Tomicus villosus^SLTe so common as to be a plague, while the 

 males are so rare as to be hardly known. 



It is hardly worth while saying anything about the proportion of 

 the sexes in certain species and even groups of insects, for the males 

 are unknown or very rare, and the females are parthenogenetic, 

 that is, fertile without sexual union ; examples of this are 

 afforded by several of the Cynipidse.f In all the gall-making 

 CynipidsB known to Mr. Walsh, the females are four or five times 

 as numerous as the males; and so it is, as he informs me, with the 

 gall-making Cecidomyiidse (Diptera). With some common species 

 of Saw-flies (Tenthredinse) Mr, F. Smith has reared hundreds of 

 specimens from larvae of all sizes, but .has never reared a single 

 male; on the other hand, Curtis says,:|: that with certain species 

 (Athalia) bred by him, the males were to the females as 6 to 1 ; 

 while exactly the reverse occurred with the mature insects of the 

 same species caught in the fields. In the family of bees, Hermann 

 Miiller^ collected a large number of specimens of many species, and 

 reared others from the cocoons, and counted the sexes. He found 

 that the males of some species greatly exceeded the females in num- 

 ber; in others the reverse occurred; and in others the two sexes were 

 nearly equal. But as in most cases the males emerge from the co- 

 coons l)efore the females, they are at the commencement of the breed- 

 ing season practically in excess. Miiller also observed that the rela- 

 tive number of the two sexes in some species differed much in differ- 

 ent localities. But as H. Miiller has himself remarked to me, these 

 remarks must be received with some caution, as one sex might more 



* Gunther's " Record of Zoological Literature," 1867, p. 260. On the excess 

 of female Lucanus, ibid. p. 250. On the males of Lucanus in England, West- 

 wood, "Modern Class of Insects,'' vol i. p. 187. On the Siagonium, ibid. p. 172. 



t Walsh in "The American Entomologist," vol. i, 1869, p. 103. F.Smith, 

 " Record of Zoological Literature," 1867, p. 328. 



t " Farm Insects," pp. 45-46. 



" Anwendung der Darwinschen Lehre Verh. d. n. V. Jahrg.," xxiv. 



