My dear M^r Darwin,

I now reply seriatim to the points noted in your letter of the 18^th inst.¹

1. The Males of the Emperor & Brimstone butterflies are visibly more numerous than the females—but with me that is no evidence that their numbers are really greater—² M^r Doubleday says of the Emperor moth (Saturnia carpini or Pavonia-Minor) he breeds more males than females, but I doubt whether you would find that the general experience.³

2. With reference to Pamphila Actaeon I can give no information.⁴

3. In many genera of moths the males have whiter underwings that the females— this renders them much more conspicuous in the evening dusk— The common Agrotis exclamationis is a good instance of this.⁵

With reference to the Oenistis quadra I have no information.⁶

4. I cannot call to mind that I ever noticed an instance of courting in the Fritillaries or Vanessæ.⁷

I have seen it in the white butterflies but then the female was sitting down calling the male— whether there had been any preliminary stages I cannot say.

5. I am not aware of any moths in which the underside is more conspicuous than the upper side (of which in Butterflies we have such a striking instance in the Green Hair Streak Thecla Rubi)— the underside of the Red Underwing is very conspicuous but not more so than the upper side.⁸

6. With a few exceptions all the most gaily coloured moths are diurnal in their habits.

7. Generally speaking there are no strongly marked sexual differences in the Tineina   in a few cases we have apterous females, then females with abbreviated wings as in Chimabacche Fagella ⁹— the differences in colour & marking are most conspicuous in the genus Elachista—but the long-horned moths of the genera Adela & Nemotois ¹⁰ are the most singularly different—whilst the differences are very slight in the wings— the antennae, eyes, palpi & clothing of the head are quite different.

Towards the end of April & beginning of May a little whitish moth Elachista rufocinerea flies along the hedge-bottoms towards dusk— these are the males on search for the female. By looking carefully on the blades of grass a female may be seen at rest— she is at once recognised by her whiter & rather more pointed wings— not unfrequently the female will be found not at rest, but sitting with her wings expanded & her body raised, fluttering her wings—& this may be noticed when there is no male near.— the males flying along the hedge-bottom come to such a female & congregate round her perhaps as many as 12 or 20— one pairs with the female & the rest fly onwards in search of other females.¹¹

In reference to your letter of Feby 21 I cannot say whether the artificial condition of life of a caged caterpillar in any way affects the sex—but I strongly incline to the belief that if collected in the pupa state the majority would still be females.¹²

I enclose you copies of some correspondence I had just had with M^r Doubleday & M^r Hellins on this subject, which I thought would interest you.¹³

Many years ago I had much diversion with the Scotch form of Lasiocampa Quercus & almost any number of males might be caught by taking a bred female on to the moors they frequented.—¹⁴ but yet I never knew the slightest difficulty in breeding a female if 2 or 3 pupæ were obtained & as M^r Hellins well puts it if you had only one pupa it was far more likely to produce a female than a male.

You will find mention of the assembling propensities of the males Bombycidae in Westwood’s Introduction to the Modern Classification of Insects vol II p. 384¹⁵

I do not think that a male insect serves more than one female

I would in conclusion throw out the suggestion that you should call the attention of Entomologists to points (on which you want information) to be observed during the coming season.¹⁶