With reference to the other Orders of insects, I have been able to collect very little reliable information. With the stag-beetle (_Lucanus cervus_) “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 six so one. With one of the Elateridæ, the males are said to be much more numerous than the females, and “two or three are often found united with one female;”[401] so that here polyandry seems to prevail. With Siagonium (Staphylinidæ), 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_ are so common as to be a plague, whilst the males are so rare as to be hardly known. In other Orders, from unknown causes, but apparently in some instances owing to parthenogenesis, the males of certain species have never been discovered or are excessively rare, as with several of the Cynipidæ.[402] In all the gall-making Cynipidæ 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 Cecidomyiiæ (Diptera). With some common species of Saw-flies (Tenthredinæ) Mr. F. Smith has reared hundreds of specimens from larvæ of all sizes, but has never reared a single male: on the other hand Curtis says,[403] that with certain species (Athalia), bred by him, the males to the females were as six to one; whilst exactly the reverse occurred with the mature insects of the same species caught in the fields. With the Neuroptera, Mr. Walsh states that in many, but by no means in all, the species of the Odonatous groups (Ephemerina), there is a great overplus of males: in the genus Hetærina, also, the males are generally at least four times as numerous as the females. In certain species in the genus Gomphus the males are equally numerous, whilst in two other species, the females are twice or thrice as numerous as the males. In some European species of Psocus thousands of females may be collected without a single male, whilst with other species of the same genus both sexes are common.[404] In England, Mr. MacLachlan has captured hundreds of the female _Apatania muliebris_, but has never seen the male; and of _Boreus hyemalis_ only four or five males have been here seen.[405] With most of these species (excepting, as I have heard, with the Tenthredinæ) there is no reason to suppose that the females are subject to parthenogenesis; and thus we see how ignorant we are on the causes of the apparent discrepancy in the proportional numbers of the two sexes.