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Darwin Correspondence Project

To Francisco de Arruda Furtado   31 October 1881

Down, | Beckenham, Kent. | (Railway Station | Orpington. S.E.R.)

Oct 31. 1881

Dear Sir

I am extremely glad that you think that you will find Wallace’s work useful.1

The egg-cases of Blatta, (as I suppose, for I am ignorant on the subject) with their white coating are curious. I scraped off some of the white matter & placed it in Acetic Acid. It effervesced, leaving a fine residue. I suppose, therefore, that it is some kind of cement or plaister. Are you sure that the place bearing the egg-case had not been white-washed, with cement or white-wash, after the egg-cases had been affixed by the insect?2

If you can observe again similar cases, I think that the fact would be worth publishing, as a good instance of skill in protection.— I can remember no such case. I have, as usual, many letters to write, so will say no more; except to wish you continued success—

Dear Sir | Yours faithfully | Ch. Darwin

Footnotes

See letter from Francisco de Arruda Furtado, 16 October 1881 and n. 2. CD had sent a copy of Alfred Russel Wallace’s Geographical distribution (Wallace 1876).
See letter from Francisco de Arruda Furtado, 22 October 1881 and n. 3. Blatta is a genus of cockroaches. Arruda Furtado had written that the chalk covering the egg casing had been chewed and applied on the sides not attached to the wall. Chalk or lime containing calcium carbonate (CaCO3) reacts with acetic acid (CH3CO2H) to form carbonic acid (H2CO3) and calcium acetate (Ca(C2H3O2)2). The carbonic acid breaks down to water and carbon dioxide, which causes the effervescing.

Bibliography

Wallace, Alfred Russel. 1876a. The geographical distribution of animals, with a study of the relations of living and extinct faunas as elucidating the past changes of the earth’s surface. 2 vols. London: Macmillan and Co.

Summary

Is glad Fd’AF will find Wallace’s work useful [see 13313].

Has examined the egg-cases of Blatta and suspects the white matter may be cement or plaster. If Fd’AF observes similar cases the fact would be worth publishing as a good instance of skill in protection.

Letter details

Letter no.
DCP-LETT-13444
From
Charles Robert Darwin
To
Francisco de Arruda Furtado
Sent from
Down
Source of text
Historical Archive of the Museums of the University of Lisbon (PT/MUL/FAF/C/01/0023)
Physical description
ALS 3pp

Please cite as

Darwin Correspondence Project, “Letter no. 13444,” accessed on 28 March 2024, https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-13444.xml

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