My dear Sir,

The publisher prepares a second impression of the first volume, even before the second has come out.¹ As you were so kind to send me proof-sheets of your second edition of the 2^d. Volume, may I ask you, if there are any alterations to be made in the first.²

I should be obliged to you very much, if you would be so kind as to answer very soon, as I promised the publisher not to keep him waiting.

My friend Donders told me you were preparing your work on the expression of the various emotions, which you mention in the “Descent”.³ When will it come?

May I be allowed to send you a few remarks on a few points contained in the 1. Vol. of the Descent of Man.

p. 360. You say that the two Orders of the Neuroptera and Orthoptera are now generally ranked as quite distinct. Now since Erickson’s remarks both of these Orders are with us brought close together,⁴ indeed the Ephemeridae,⁵ Libellulidae⁶ Perlidae⁷ are ranked amongst the Orthoptera, and only the Phryganidae,⁸ Mantispa, Myrmadleon, Ascalaphus,⁹ Sialid,¹⁰ Embid¹¹ are left by themselves as Neuroptera. Thus your instances of Ephemeridae, Libellulidae (p 261a) would come according to our generally accepted classification under “Orthoptera”.¹²

On p. 261 you mention the difference of colour between the two sexes of Oecanthus nivalis, an American form.¹³ The same difference, though not quite as great perhaps, is seen with our European Oecanthus pellucidus.¹⁴ Comp. Fischer Orthoptera Europaea. p 165, which statement I can confirm from observation.¹⁵

To page 416 I may state the fact, that I know some persons who instantly feel a nauseous incomfortable sensation about their stomach, as soon as they behold an “ugly coloured” toad or caterpillar, so that they are warned by instinct not to touch (or devour) them¹⁶

p. 314. With regard to the proportional numbers of the two sexes with Insects it struck me, that it is sometimes not only very difficult but indeed impossible to count the males and females, as with some of these, especially Cynipidae, Tenthrediridae, Psocus and some others Parthenogenesis takes place, so that there are entire generations consisting only of females without a trace of a male   The case is the same as with some of the lower Crustaceans.¹⁷ I fully appreciate your mentioning the asexual reproduction occurring with some of these forms. But I think in giving facts on the proportional numbers of the sexes you might perhaps lay a little more stress on the fact that in very many of these cases any numeration must be incorrect as long as the observer has not satisfied himself that in the case just under his notice Parthenogenesis has not taken place

Believe me, My dear Sir, | Yours most faithfully | Prof J. Victor Carus

Leipzig, 22. April | 1871.