Dear Sir.

I hope you will kindly excuse the liberty, I take in calling your attention to the latest work of my countryman Prof. O. Heer, “Die Urwelt der Schweiz”. Zürich 1865.—¹ On pg 599 & seq., in a footnote, the author refers to your valuable observation, that f. sanguinea keeps less slaves in this country than in Switzerland;² but he adds. ‘es sind diess aber unbedeutende Unterschiede, die nach den Jahreszeiten und auch nach den verschiedenen Stöcken wechseln”. etc.—³

If it does not give you too much trouble, I should feel much obliged by your informing me at your convenience, to what circumstances you attribute the fact that these slaves are captured in greater numbers in Switzerland than in England.—

It seems to me that British ants, being through climate etc. in a harder struggle for life & food, ought rather be found to keep more slaves to attend to their wants, than their Swiss brethren, which have a richer fauna & flora to fall back upon & therefore less labour to perform.—

Apologizing for my intruding upon you, I am, | Dear Sir, | your’s obediently | Albert Müller

Charles Darwin Esq^re.