Finds no absolute differences in size of sexes of Copridae. Gives several other genera in which males are larger than females.
Confirms his view of stridulation organ of house cricket. [see Descent 1: 354–5.]
Tells CD of a powerful convert to Darwinism: H. von Kiesenwetter of Berlin.
Royal Geographical Society | 15, Whitehall Place, S.W.
Feb 26 1868
My dear Mr Darwin
I have examined more than 100 species of all the genera of horned Copridæ & find there is no absolute difference in size between male & female. This conclusion would not perhaps be arrived at, if a good series of each species were not at hand for comparison, as the Copridæ vary unusually in size & ill-developed males smaller than females are very common; but fully developed individuals of both sexes always agree pretty well in size.—
I have looked at a good many Dynastidæ & find the males in some genera a little longer than the females; in bulk they are much greater than the females, owing to horns & their supports, but the difference in length & breadth exclusive of horns, when they come to be measured is not much. The genera Dynastes & Megasoma may be safely quoted as those in which this disparity in size is less subject to doubt.
I have now no longer a large collection of Orthoptera; but will profit by my next visit to B.M. to notice if there is any sexual difference in colours.
I have, since I last wrote, re-examined a male house cricket & can confirm my former statement that there is no difference in shape of the two wing cases at the part where the stridulating organs are situated. There is also very little difference in the form of the organ itself on the left & right wing case, one however is probably scored across & the other smooth, I must examine them again under microscope.
We have gained a powerful convert to Darwinianism in M
Yours sincerely | H W Bates
- f1 5936.f1CD had enquired about the differences in size between males and females in various beetles (see letter to H. W. Bates, 22 February  and n. 6). The Copridae are now subsumed in the family Scarabaeidae.
- f2 5936.f2In Descent 1: 347, CD noted that males were larger than females in the genera Dynastes and Megasoma.
- f3 5936.f3See letter to H. W. Bates, 22 February  and n. 8. Bates refers to the British Museum. Orthoptera is the order of grasshoppers, crickets, and their allies.
- f4 5936.f4In Descent 1: 353, CD remarked that in males of the family Achetidae (now Gryllidae, crickets) both wing covers have the same structure.
- f5 5936.f5Bates refers to Ernst August Hellmuth von Kiesenwetter, and to Kiesenwetter 1867. CD's heavily annotated copy is in the Darwin Pamphlet Collection--CUL. Chrysomelidae are leaf-beetles.