To J.-H. Fabre   21 January 1881

Dear & Honoured Sir

I am much obliged for yr very interesting letter. Your results appear to me highly important, as they eliminate one means by which animals might perhaps recognise direction; & this from what has been said about savages, & from our own consciousness, seemed the most probable means.¹

If you think it worth while, you can of course mention my name in relation to this subject.

Should you succeed in eliminating a sense of the magnetic currents of the earth, you would leave the field of investigation quite open. I suppose that even those who still believe that each species was separately created, would admit that certain animals possess some sense by which they perceive direction, & which they use instinctively. On mentioning the subject to my son George,² who is a mathematician & knows something about magnetism, he suggested making a very thin needle into a magnet; then breaking it into very short pieces, which would still be magnetic, & fastening one of these pieces with some cement on the thorax of the insect to be experimented on.

He believes that such a little magnet, from its close proximity to the nervous system of the insect, would affect it more than would the terrestial currents.

I have received your essay on Halictus, which I am sure that I shall read with much interest.³

With much respect, I remain | Dear Sir | Yours very faithfully Charles Darwin