From Henry Doubleday 5 February 1857
Feby 5th 1857.
My dear Sir,
I am truly glad to find that the few insects which I sent were acceptable.— you are most heartily welcome to them and I regret that you did not write before my stock of duplicates was so much reduced— I could then have sent you varieties of several other species.
If all is well this year, I shall be most happy to send any specimens that I may obtain likely to interest you.
The variations of colour and markings in the Peronea are really astonishing— Haworth and the late J. F. Stephens did not at all understand the two species—Cristana and Hastiana— they created thirty or forty species founded upon the variations in colour and markings.1 Very soon after I had paid any attention to them I felt convinced that all these reputed species would sink into two. I believe at that time every Entomologist in London thought that my 〈o〉pinion was 〈err〉oneous—but they now all admit that I was right.
In my last letter I alluded to a Geometra—Harpalyce Russata— there is an allied species—immanata of Haworth—typical specimens of which so much resemble those of Russata that no one but an Entomologist could separate them.— This species runs through similar variations to those of Russata—with the exception of the yellow-banded variety—the Comma-notata of Haworth.— The central fascia in immanata varies from white through all shades of grey to black, but is never yellow.
In answer to your query as to whether I can give any good instances of species varying in one locality and not in another I may mention the above-named insect H Russata— Mr Logan2 tells me that at Edinburgh he only takes the type—that it does not vary at all.
There is another Geometra—Angerona prunaria the typical specimens of which are pure orange with slight dusky irrorations— in the south of England a clouded variety with the wings broadly margined with deep brown is almost as common as the type— I beli〈eve〉 this variety 〈ne〉ver occurs in the north of England— Many species of Lepidoptera are always double-brooded—that is there are two distinct broods in each year— in many species there is little or no difference between the individuals of the two broods—but in others the differences in size and colour are constant and striking— Selenia illustraria and S. illunaria may be mentioned as instances— the spring broods appear in April—and the specimens are large and highly-coloured— from the eggs of these the second brood of moths comes forth in July— these are always much smaller than the vernal specimens and differently coloured— from these small summer specimens we of course have the large specimens the following spring—3
In the common White butterflies—Pieris brassicæ and P. Rapæ the reverse is the case— the vernal specimens are always smaller and more faintly marked than the summer ones.
I enclose a portion of my list with the varieties of the two species of Peronea 4 —all the varieties of Hastiana, I and others have reared in numbers from larvæ found upon sallows at the same time and which were exactly alike—and the perfect insects copulate indiscriminately—so that there is not a shadow of doubt that they all belong to one species The larva of Peristera is unknown but there is not the slightest doubt of all the varities belonging to one species as they appear simultaneously and every intermediate shade may be found. They differ from Hastiana in always having a tuft of Scales on the wing— All the varities of Peronea are liable, like most other species, to slight variations in size— I may just add that it extremely difficult to rear larvae of the minute moths from the eggs—but three or four years I confined two females of P. Hastiana under gauze upon a young sallow in our garden and upon which I had never seen a larva of this species before and in August I took a number from the curled up leaves and bred the greater part of the varieties— I have thus stated a few facts but can throw little or no light upon this interesting subject— There was nothing particular about the packing of the box—5 I always send parcels to the post done up in a similar manner—
I shall always be most happy to hear from and glad to serve you in any way in my power and with best wishes believe me | My dear Sir | Yours very Sincerely | Henry Doubleday C Darwin Esq
The variations of Peronea caused A. H. Haworth and J. F. Stephens to create 30 or 40 species based on colour and markings. HD was first to be convinced these would be reduced to two.
Discusses species that closely resemble one another;
cites species that differ in variation in different localities;
in some double-brooded species the broods differ markedly in size and colour.
Encloses his list of varieties of Peronea.