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Darwin Correspondence Project

From C. S. Bate   31 July 1869


July 31. 69

My dear Sir

I find your letter upon my return home after a short absence.—1 In carcinas mænas the male carries the female about hugging her with the dorsal surface against his ventral surface—seeking apparently some quiet place of concealment, this continues longer or a shorter time until the female moults, when immediately copulation takes place & continues some day or two probably until the integument of the female becomes hard & calcareous:— Copulation takes place face to face—2

Crustacea—not parasitic or entomostracous are I think generally larger than the female3   Certainly so in the Brachyura to a marked degree—generally—But not conspicuously so in the Anomoura and Macroura—4

In the Amphipoda & Isopoda the males are the larger except in Parasitic genera5—in which they are generally smaller— In the Ento-mostracous Crustaceæ I am less certain But I think variable

I hope that my information is of use as it always pleases me to find it so

Believe me yours sincerely | C. Spence Bate

CD annotations

1.1 I find … calcareous:— 1.6] crossed pencil
Top of letter: ‘Size’ pencil


CD’s letter to Bate has not been found.
Carcinus maenas is the common shore crab. For Bate’s earlier letter on a male of this species seen fighting a crab of a different genus, see the letter from C. S. Bate, 1 February 1869.
In Descent 1: 332, CD cited Bate on the relative sizes of the sexes in Crustacea. Entomostraca was the name used to refer to all crustaceans other than Malacostraca (Leftwich 1973).
Brachyura (true crabs) and Anomura (a group that includes hermit crabs) are now infraorders of the order Decapoda, while Macrura was the order that included shrimp and long-tailed lobsters. All the above belong to the superorder Eucarida.
Amphipoda and Isopoda are now orders within the superorder Peracarida.


Descent: The descent of man, and selection in relation to sex. By Charles Darwin. 2 vols. London: John Murray. 1871.

Leftwich, A. W. 1973. A dictionary of zoology. 3d edition. London: Constable.


Mating practice of Carcinus maenas [see Descent 1: 331].

Difference in size in sexes of Crustacea.

Letter details

Letter no.
Charles Spence Bate
Charles Robert Darwin
Sent from
Source of text
DAR 82: A72–3
Physical description
3pp †

Please cite as

Darwin Correspondence Project, “Letter no. 6847,” accessed on 24 September 2021,

Also published in The Correspondence of Charles Darwin, vol. 17