My dear M^r Darwin

I could not myself remember any case of female insects being very conspicuously more numerous than the males & therefore put the question, as you desired to the Entomological Society, last night. Some facts & good opinions were elicited:—¹

M^r Stainton said that observations of numerical proportion of the sexes, in collecting were quite unreliable, for it was a well-known fact that in collecting Tineina moths the females were nearly in all species very scarce, whereas in breeding the females proved to be more numerous—as 2 to 1 to the males.² Mr F. Smith also stated that observations in the field were of little value. He quoted some most interesting experiments he was making in breeding some British Sawflies—all the individuals turning out to be females.³ These I think will prove to be cases of parthenogenesis: M^r Smith will write to you himself.

Other members gave these cases:—

Tomicus villosus (bark Coleopter of the oak)⁴

no male found by Ratzeburg during many years observation⁵

Tomicus dispar— an English species

males exceedingly rare⁶

Miana arcuosa⁷— an English moth—

males fly in great

numbers over damp meadows in many places—females only

one or two in a season

Apatania muliebris⁸  

an English Neuropterous insect  

hundreds of females found

during last two years— no male yet found

In Hemerobiidæ according to Maclachlan females are much more numerously found than the males.⁹

One of the above cases I have mentioned by mistake—it being the reverse illustration—males more numerous than females.— Plenty of cases can be mentioned of males occurring more numerous; but after the strongly expressed opinions of Stainton & Smith & the case of the Tineina (which was confirmed by other able observers, Mr F. Bond among them)¹⁰ I must say I shall hereafter hesitate to accept any fact, without reserve, of sexual disparity in numbers without the species are actually bred. Although the cases of vast majority of ♂ butterflies in hot countries seem pretty clear, yet it is possible the females may, in some unaccountable manner, elude observation.

Perhaps in selecting species for figuring in your next work, it would be better to chose the most wonderful, altho’ they may not be British. The Chilian stag beetle Chiasognathus, would surprise people more than our common insect.¹¹ I am now reading your two Volumes. Pangenesis I have read once & must read again before I thoroughly understand it.¹² A friend tells me the same.

Yours sincerely | H W Bates