From Robert McLachlan   20 February 1871

My dear Sir

I have to thank you heartily for your very handsome present the “Descent of Man”.¹ When I have studied the vols. I will forward to you any additional information bearing upon the subject, as treated by you, that may occur to me.²

I content myself now with one remark. You have put considerable stress upon the inequality in the chelae, jaws &c of certain Crustacea & Beetles.³ Now a curious instance occurs in a small Caddis-fly—Setodes interrupta F.—in which the anal appendices of the ♂ present great inequality— I have examined many specimens, & in all I find that the left hand app. intermed. is nearly twice the length of the right (See. Trans. Ent. Soc. 3^rd series, vol. 5, p. 122).⁴ Probably the appendices of 2000 species of Neuroptera have been examined by me, & in no other case have I observed a like inequality.

Your’s very faithfully | R. M^c. Lachlan