My life : a record of events and opinions - Wallace-online.org

—228 MY LIFEescape dangers, I can hardly attribute their brightcolour in other cases to mere physical conditions.Bates says the most gaudy caterpillar he ever saw inAmazonia was conspicuous at the distance of yards,from its black and red colours, whilst feeding onlarge, green leaves. If any one objected to malebutterflies having been made beautiful by sexualselection, and asked why they should not have beenmade beautiful as well as their caterpillars, whatwould you answer ? I could not answer, but shouldmaintain my ground. Will you think over this, andsome time, either by letter or when we meet, tell mewhat you think " ?On reading this letter, I almost at once saw whatseemed to be a very easy and probable explanationof the facts. I had then just been preparing forpublication (in the Westminster Review) my ratherelaborate paper on "Mimicry and Protective Colouring,"and the numerous cases in which speciallyshowy and slow-flying butterflies were known to havea peculiar odour and taste which protected them fromthe attacks of insect-eating birds and other animals,led me at once to suppose that the gaudily colouredcaterpillars must have a similar protection. I hadjust ascertained from Mr. Jenner Weir that one ofour common white moths {Spilosoma menthrasti)would not be eaten by most of the small birds in hisaviary, nor by young turkeys. Now, as a white mothis as conspicuous in the diisk as a coloured caterpillarin the daylight^ this case seemed to me so much ona par with the other that I felt almost sure myexplanation would turn out correct. I at once wroteto Mr. Darwin to this effect, and his reply, datedFebruary 26, is as follows :