I One Day Met With A Curious Example Of Failure Of Instinct, Which, By Showing It To Be Fallible, Renders It Very Doubtful Whether It Is Anything More Than Hereditary Habit, Dependent On Delicate Modifications Of Sensation.

Some sailors cut down a good-sized tree, and, as is always my practice, I visited it daily for some time in search of insects.

Among other beetles came swarms of the little cylindrical woodborers (Platypus, Tesserocerus, &c.), and commenced making holes in the bark. After a day or two I was surprised to find hundreds of them sticking in the holes they had bored, and on examination discovered that the milky sap of the tree was of the nature of gutta-percha, hardening rapidly on exposure to the air, and glueing the little animals in self-dug graves. The habit of boring holes in trees in which to deposit their eggs, was not accompanied by a sufficient instinctive knowledge of which trees were suitable, and which destructive to them. If, as is very probable, these trees have an attractive odour to certain species of borers, it might very likely lead to their becoming extinct; while other species, to whom the same odour was disagreeable, and who therefore avoided the dangerous trees, would survive, and would be credited by us with an instinct, whereas they would really be guided by a simple sensation.

Those curious little beetles, the Brenthidae, were very abundant in Aru. The females have a pointed rostrum, with which they bore deep holes in the bark of dead trees, often burying the rostrum up to the eyes, and in these holes deposit their eggs.

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