314 
THE PRINCIPLES OF 
Part H 
With Siagonium (Staphylinidaj), 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 hark-feeding Tomicus villosus are so common as t* 3 
he a plague, whilst the males are so rare as to be hardly know 3 - 
In other Orders, from unknown causes, but apparently in some inf 
stances owing to parthenogenesis, the males of certain species have 
never been discovered or are excessively rare, as with several of tb c 
Cynipid®. 67 In all the gall-making Cynipidaj known to Mr. Wahhi 
the females are four or five times as numerous as the males ; and 
it is, as he informs me, with the gall-making Cecidomyikn (Dipterft)- 
With some common species of Saw-flies (Tenthredina) Mr. 
Smith has reared hundreds of specimens from larva of all siM 6 ' 
l)ut has never reared a single male : on the other hand Curtis say& 
that with certain species (Athalia), bred by him, the males to tl' e 
females were as six to one ; whilst exactly the reverse occurred wi^ 
the mature insects of the same species caught in the fields. Wi^ 
the Neuroptera, Mr. Walsh states that iu many, but by no mean 9 
in all, the species of the Olonatous groups (Ephemerina), there is* 
great overplus of males : in the genus Hctierina, also, the males ar® 
generally at least four times as numerous as the females. In certain 
species in the germs Complies the males are equally numerous 
whilst in two other species, the females are twice or thrice 
numerous as the males. In some European species of Psocus tbo®” 
sands of females may bo collected without a single male, whil st 
with other species of the same genus both sexes are common. 69 I* 
England, Mr. Mac Lachlan has captured hundreds of the feioak 
Apatania muliebris, but has never seen the male; and of J3ore“ s 
hyemalis only four or five males have been here seen. 70 With mo® 1 
of these species (excepting, as I have heard, with the Tenthredin: 1 ') 
there is no reason to suppose that the females are subject to parth r 
nogenesis ; and thus we sec how ignorant wc are on the causes of ^ 
apparent discrepancy in the proportional numbers of the two scs 1 *; 
in the other Classes of the Articulata 1 have been able to coll 1 ** 
still less information. With Spiders, Mr. Blackwall, who has cab' 
fully attended to this class during many years, writes to me tfc® 1 
the males from their more erratic habits are more commonly se eIJ ’ 
67 Walsh, in ‘ The American Entomologist,’ vol. i. 1869, p. 103. F. 
‘ Record of Zoological Literature,’ 1867, p. 328. 
88 ‘ Farm Insects,’ p. 45-46. 
69 ‘ Observations on N. American Neuroptera,’ by H. Hao-en and B. 
Walsh, ‘ Proc. Ent. Soc. Philadelphia,’ Oct. 1863, p. 168, 223, 239. 
70 ‘ Proc. Ent. Soc. London,’ Feb. 17, 1868. 
