9, St. Mark's Crescent
N.W.
Septr. 18th. [1868]1
Dear Darwin
The more I think of your views as to the colours of females, the more difficulty I find in accepting them or even in clearly understanding them. As you are now working at the subject I hope it will not interrupt you to hear "Counsel on the other side".
1. You admit, I think, that the female in birds & insects requires more protection, & in the latter case, for a longer time.2
2. Now if the male & female were distinct species with different habits and organizations you would at once admit that a difference of colour, tending to make that one less conspicuous to which concealment was evidently most necessary, had been acquired by Nat[ural]. Select[ion].
3. But you admit also & in fact maintain strongly that variations occurring in one sex may be and often are transmitted to that sex only.3 There is therefore nothing to prevent Nat. Select. acting on the two sexes as if they were two species.
[2] 4. But you admit that many species are protected by general or special tints or markings,— & that such protection has been acquired by Nat. selection.
5. When however the female only has exactly similar protective tints or markings, you deny that N. select. has given these tints to her alone. I cannot see why.
6. Your objection that the same protection would to a certain extent be useful to the male also seems to me quite unsound,4 and directly opposed to your own doctrines. For you urge strongly, that Nat. Select. can never improve an animal beyond its needs. So that even if we admit abundant variation of colour in the male, nat. select. will not bring him to resemble the female in protective tints (except where her variations are always transmitted to him) because the difference in their colours balances the difference in their organizations & habits. If it did more than this, Nat. Select. would produce something superfluous, wh[ich]. it cannot do.
[3] 7. The fact that in almost all protected groups the females are equally brilliant & conspicuous with the males, shews I think a tendency to transference of colour from one sex to the other when this tendency is not injurious. Or perhaps the protection may be acquired, because this tendency to uniform colour in the sexes exists. This will apply to the gay birds with nests in holes &c. where the gay colours may have been acquired by the males through sexl. selection & transferred to females by laws of inheritance5. This I believe is your view; but it fails in cases of the mimicking Leptalis,6 as there the males certainly did not acquire their gay colours through sexual selection.
Now for the more special case
8. In the weak — and slow-flying Leptalis both sexes mimic Heliconidae7
9. In the more powerful and swifter Papilio Pieris and Diadema,8 the female [4] alone generally mimics the protected group.
10. In these cases the female often has acquired more bright varied and conspicuous colours than the male,—sometimes as in Pieris pyrrha9 &c. remarkably so.
11. Not a solitary case is known of any male insect alone mimicking a protected group.
12. Yet colour is more frequently developed in males, & variations of colour are always ready for purposes of sexual or other selection.
13. The reason of this apparent anomaly is evident, on the principle that each species and each sex can only be modified by selection just so much as is absolutely necessary, — not a step further.
One species indeed may be more perfectly adjusted than another, because that other may dwindle & die out without directly affecting it; — but one sex cannot be perfected by Nat. Select. [5]10 much beyond the other, beyond because directly it is so in the least degree, then the deficiency of the other pulls it back — the whole struggle for existence of the species falls upon the less perfect sex, and rigid selection soon brings that sex up to the same level as its partner.
14. It follows, that a male insect or bird, being by structure or habits less exposed to danger than its partner, is, to that extent, better adjusted to conditions. The protective colouring of the female balances this inequality in many cases, & Nat. select. can do no more than balance the two; it cannot give the male the protection he does not absolutely require, although he may sometimes gain it by inheritance from his partner.
[6] 15. I cannot think that an objection derived from cases in which the protection of colour does not appear to exist (like that of the fish &c.) have any weight at all. Colour is only one of many modes of protection, and this kind of protection is never acquired when another already exists.
Exactly a similar objection is made to the whole doctrine of "mimicry". Why, it is asked, are there any white and yellow, quite unprotected (apparently) Leptalis? We answer, we do not know, but we firmly believe that they have some protection which the others have not, & wh[ich]. exactly balances it. So, out of about 500 species of Papilionidae, the females of about a dozen are undoubted "mimickers". Are we to deny that the need of protection has produced this mimicry because [7] we cannot in the immense balance of species point out the exact protection of another kind, which enables them to do without it?
I am afraid I have not put my argument very clearly or consecutively, but I am at present utterly unable to see my way to any other conclusions than those here indicated.
Your view appears to be me to be opposed to your own laws of Nat. Selectn. & to deny its power & wide range of action. Unless you deny that the general dull hues of female birds and insects are of any use to them, I do not see how you can deny that Nat. Select. must tend to increase such hues, and to eliminate brighter ones. I could almost as soon believe that the [8] structural adaptations of animals & plants were produced by, "laws of variation & inheritance" alone, as that what seem to me equally beautiful & varied adaptations of colour sh[oul]d. be so produced.
There is a difficulty I have on another subject. Admitting sexual selection in its fullest extent as having developed male weapons and ornaments, and in birds colour: how is it that there is so little sexual colour or marking in Mammals? Have they no taste for colour? Again about insects. Is there any evidence to show that female insects ever reject or choose males by colour, or at all? It seems difficult to believe that they do.
I am sorry you troubled yourself to return the box.11 It was not worth it. Do not trouble yourself to answer this at length, unless you like to do so.
Just say whether it produces any effect or no.
Yours very faithfully | Alfred R. Wallace [signature]
Status: Edited (but not proofed) transcription [Letter (WCP4082.4029)]
For more information about the transcriptions and metadata, see https://wallaceletters.myspecies.info/content/epsilon
9 St. Mark's Crescent N.W.
Septr. 18th. [1868]1
Dear Darwin,
The more I think of your views as to the colours of females, the more difficultly I find in accepting them, and as you are now working at the subject I hope it will not interrupt you to hear "counsel on the other side".
I have a "general" and a "special" argument to submit.
1. Female birds & insects are generally exposed to more danger than the male, and in the case of insects their existence is necessary for a longer period.
2. They therefore require in some way or other a special balance of protection.
3. Now if the male & female were distinct species, with different habits & organizations, you would I think at once admit, that a difference of colour serving to make that one less conspicuous which evidently required more protection than the other, had been acquired by nat[ural]. select[io]n.
4. But you admit that variations appearing in one sex are transmitted (often) to that sex only: [2] there is therefore nothing to prevent nat[ural]. select[ion]. acting on the two sexes as if they were two species.
6. [sic]2 Your objection that the same protection would to a certain extent be useful to the male, seems to me utterly unsound, & directly opposed to your own doctrine to convincingly urged in the "Origin",3 "that N[atural]. Sel[ectio]n. never can improve an animal beyond its needs." So that admitting abundant variation of colour in the male, it is impossible that he can be brought by nat[ural]. select[ion]. to resemble the female (unless her variations are always transmitted to him) because the difference of their colours is to balance the difference in their organizations & habits, — and nat[ural]. select[ion]. can only balance not give to the male different needs, induceing[?] different degrees of more than is needed to affect that balance. rigidity in selection, can not produce the same result.
7.4 The fact that in almost all protected groups the females perfectly resemble the males, shews I think a tendency to transference of colour from one sex to the other where this tendency is not injurious. Or perhaps the protection is acquired because this tendency exists. I admit therefore then[?] in the case of concealed nests they [sic] habits may have been acquired for protection.
[3] Now for the special case.5
8. In the very weak flying Leptalis both sexes mimic Heliconidae [Heliconiidae]
9. In the much more powerful Papilio [,] Pieris and Diadema it is generally the female only that mimics Danaida.
10. In these cases the females often acquire more bright & varied colours than the male, sometimes as in Pieris pyrrha conspicuously so.6
11. No single case is known of a male Papilio or Pieris or Diadema or any other insect alone, mimicking a Danais, &c.
12. But colour is more frequent in males, and variations always seem ready for purposes of sexual or other selection.
13. The plain explanation fair inference seems to be that given in pp. [propostion] 5 of the general argument, — viz. that each species & each sex can only be modified by selection just as far as is absolutely necessary, not a step farther. A male, being by structure & habits less exposed to danger & less requiring protection than the female cannot have more protection given to it [4] by nat[ural]. select[io]n., but a female must have some extra protection to balance the greater danger, & she rapidly acquires it in one way or another.
15. [sic]7 An objection derived from cases like male fish which seem to require protection, yet having brighter colours, seems to me of no more weight than is that of the existence of many white & unprotected species of Leptalis, to Bates'8 theory of mimicry; — that only one or two species of butterfly perfectly resemble leaves, or, that the instincts or habits or colours that seem essential to the preservation of one animal seems are often totally absent in an allied species.
Status: Edited (but not proofed) transcription [Author’s draft (WCP4082.4989)]
For more information about the transcriptions and metadata, see https://wallaceletters.myspecies.info/content/epsilon
Draft of a letter to C. Darwin, found among Dr Wallace’s papers
9 St. Mark’s Crescent N.W. Sept. 18th 18691
Dear Darwin
The more I think of your views as to sexual the colours of females, the more difficulty I find in accepting them, and as you are now working at the subject I hope it will not interrupt you to hear "counsel on the other side".
I have a "general" and a "special" argument to submit.
1.Female birds & insects are generally exposed to more danger than the male, and in the case of insects their existence is necessary for a longer period.
2. They therefore require in some way or other a special balance of protection.
3. Now if the males & female were distinct species, with different habits & organizations, you would I think at once admit, that a difference of colour serving to make that one less conspicuous which evidently required more protection than the other, had been acquired by nat[ural] selct[io]n.
4. But you admit that variations appearing in one sex are transmitted (often) to that sex only. there is therefore nothing to prevent nat.[ural] select.[tion] acting on the two sexes as if they were two species.
5. Your objection that the same protection would to a certain extent be useful to the male, seems to me utterly unsound, & directly opposed to your own doctrine so convincingly argued in the "Origin"2, "that N[atural] Sel[ectio]n never can improve an animal beyond its needs". So that admitting abundant variation of colour in the male, it is impossible that he can be brought by nat.[ural] select.[tion] to resemble the female (unless her variations are always transmitted to him) because this difference of their colours is to balance the difference in their organizations & habits,- and nat.[ural] select.[tion] can not give to the male more than is needed to affect that balance.
6. The fact that in almost all protected groups the females perfectly resemble the males, shows I think a tendency to transference of colour from one sex to the other when this tendency is not injurious
[2] Draft of letter to C. Darwin, Sep. 18, 1869.)
Or perhaps the protection is acquired because this tendency exists. I admit therefore then in the case of concealed visits they (habits) have been acquired for protection.
Now for the special case.
7. In the very weak flying Leptalis both sexes mimic Heliconidae.
8. In the much more powerful Papilio Pieris and Diadema it is generally the female only that mimics Danaida.
9. In these cases the females often acquire more bright & varied colours than the male. Sometimes as in Pieris pyrrha conspicuous so.
10. No single case is known of a male Papilio Pieris, Diadema (or any other insect?) alone mimicking a Danais &c.
11. But colour is more frequent in males, and variations always seem ready for purposes of sexual or other selection.
12. The fair inference seems to be that given in p[roposition].5 of the general argument, — viz. that each species & each sex can only be modified by selection just as far as is absolutely necessary, not a step farther. A male, being by structure & habits less exposed to danger & less requiring protection than the female cannot have more protection given to it by nat[ural] select[io]n, but a female must have some extra protection to balance the greater danger, & she rapidly acquires it in one way or another.
13. An objection derived from cases like male fish which seem to require protection, yet having brighter colours, seems to me of no more weight than is that of the existence of many white & unprotected species of Leptalis; to Bates’ theory of mimicry;— that only one or two species of butterflies perfectly resemble leaves, or, that the instincts or habits or colours that seem essential to the preservation of one animal are often totally absent in an allied species.
[No signature; author’s draft of letter]
Status: Draft transcription [Transcription (WCP4082.4508)]
For more information about the transcriptions and metadata, see https://wallaceletters.myspecies.info/content/epsilon
[1]1
Draft of a letter to C.Darwin, found among Dr Wallace's papers)
9, St.Mark's Crescent N.W. Sept. 18th 1869
Dear Darwin The more I think of your views as to sexual the colours of females, the more difficulty I find in accepting them, and as you are now working at the subject I hope it will not interrupt you to hear "counsel on the other side".
I have a "general" and a "special" argument to submit.
1. Female birds & insects are generally exposed to more danger than the male, and in the case of insects their existence is necessary for a longer period.
2. They may there require in some way or other a special balance of protection.
3. Now if the male & female were distinct species, with different habits & organizations, you would I think at once admit, that a difference of colour serving to make that one less conspicuous which evidently required more protection than the other, had been acquired by nat. select'n.
4. But you admit that variations appearing in one sex are transmitted (often) to that sex only: there is therefore nothing to prevent nat. select. acting on the two sexes as if they were two species.
5. Your objection that the same protection would to a certain extent be useful to the male, seems to me utterly unsound, & directly opposed to your own doctrine so convincingly urged in the "Origin", "that N.Sel'n never can improve an animal beyond its needs". So that admitting abundant variation of colour in the male, it is impossible that he can be brought by nat. select. to resemble the female (unless her variations are always transmitted to him) because the difference of their colours is to balance the difference in their organizations & habits,— and nat.select. can not give to the male more than is needed to effect that balance.
6. The fact that in almost all protected groups the females perfectly resemble the males, shews I think a tendency to transference of colour from one sex to the other when this tendency is not injurious. [2] [3]2
Draft of letter to C.Darwin, Sep.18,1869.)
Or perhaps the protection is acquired because this tendency exists. I admit (?) therefore (?) then (that?) in the case of concealed nests they (habits) may have been acquired for protection.
Now for the special case.
7. In the very weak flying Leptalis both sees mimic Heliconidae.
8. In the much more powerful Papilio Pieris and Diadema it is generally the female only that mimics Danaida.
9. In these cases the females often acquire more bright and varied colours than the male. Sometimes as in Pieris pyrrha conspiculously so.
10. No single case is known of a male Papilio Pieris, Diadema orany (or any other insect)? alone mimicking a Danais &c.
11. But colour is more frequent in males, and variations always seem ready for purposes of sexual or other selection.
12. The fair inference seems to be that given in pp.5 of the general argument,— viz. that each species & each sex can only be modified by selection, just as far as is absolutely necessary, not a step farther. A male, being by structure & habits less exposed to danger & less requiring protection than the female cannot have more protection given to it by nat. select'n., but a female must have some extra protection to balance the greater danger, & she rapidly acquires it in one way or another.
13. An objection derived from cases like male fish which seem to require protection, yet having brighter colours, seems to me of no more weight than is that of the existence of many white & unprotected species of Leptalis, to Bates' theory of mimicry:— that only one or two species of butterflies perfectly resemble leaves, or, that the instincts or habits or colours that seem ess essential to the preservation of one animal are often totally absent in an allied species. [4]
Status: Draft transcription [Transcription (WCP4082.4990)]
For more information about the transcriptions and metadata, see https://wallaceletters.myspecies.info/content/epsilon
[1] [p. 223]
9 St. Mark's Crescent, N.W.
September 18, 1868
Dear Darwin,—The more I think of your views as to the colours of females, the more difficulty I find in accepting them, and as you are now working on the subject I hope it will not interrupt you to hear "counsel on the other side."
I have a "general" and a "special" argument to submit.
1. Female birds and insects are generally exposed to more danger than the male, and in the case of insects their existence is necessary for a longer period.
2. They therefore require in some way or other a special balance of protection.
3. Now, if the male and female were distinct species, with different habits and organisations, you would, I think, at once admit that a difference of colour serving to make that one less conspicuous which evidently required more protection than the other had been acquired by Natural Selection.
4. But you admit that variations appearing in one sex are transmitted (often) to that sex only: there is therefore [2] [p. 224] nothing to prevent Natural Selection acting on the two sexes as if they were two species.
5. Your objection that the same protection would to a certain extent be useful to the male, seems to me utterly unsound, and directly opposed to your own doctrine so convincingly urged in the "Origin," "that Natural Selection never can improve an animal beyond its needs." So that admitting abundant variation of colour in the male, it is impossible that he can be brought by Natural Selection to resemble the female (unless her variations are always transmitted to him), because the difference of their colours is to balance the difference in their organisations and habits, and Natural Selection cannot give to the male more than is needed to effect that balance.
6. The fact that in almost all protected groups the females perfectly resemble the males shows, I think, a tendency to transference of colour from one sex to the other when this tendency is not injurious.
Or perhaps the protection is acquired because this tendency exists. I admit therefore in the case of concealed nests they [habits] may have been acquired for protection.
Now for the special case.
7. In the very weak-flying Leptalis both sexes mimic Heliconidae.
8. In the much more powerful Papilio, Pieris, and Diadema it is generally the female only that mimics Danaida.
9. In these cases the females often acquire more bright and varied colours than the male. Sometimes, as in Pieris pyrrha, conspicuously so.
10. No single case is known of a male Papilio, Pieris, Diadema (or any other insect>) alone mimicking a Danais, etc. [3] [p. 225]
11. But colour is more frequent in males, and variations always seem ready for purposes of sexual, or other selection.
12. The fair inference seems to be that given in proposition 5 of the general argument, viz. that each species and each sex can only be modified by selection just as far as is absolutely necessary, not a step farther. A male, being by structure and habits less exposed to danger and less requiring protection than the female, cannot have more protection given to it by Natural Selection, but a female must have some extra protection to balance the greater danger, and she rapidly acquires it one way or another.
13. An objection derived from cases like male fish, which seem to require protection, yet having brighter colours, seems to me of no more weight than is that of the existence of many white and unprotected species of Leptalis to Bate's theory of mimicry, that only one or two species of butterflies perfectly resemble leaves, or that the instincts or habits or colours that seem essential to the preservation of one animal are often totally absent in an allied species.
Status: Draft transcription [Published letter (WCP4082.5994)]
For more information about the transcriptions and metadata, see https://wallaceletters.myspecies.info/content/epsilon
Please cite as “WCP4082,” in Beccaloni, G. W. (ed.), Ɛpsilon: The Alfred Russel Wallace Collection accessed on 26 April 2024, https://epsilon.ac.uk/view/wallace/letters/WCP4082