Monday, June 2, 2008

Fraudator tripartitus

The “life-long imposter” I mentioned earlier now wriggles onto center stage — ready, in its very infancy, to carry out its first swindle. The triple-ruse hawk moth worm (Fraudator tripartitus) possesses all the qualities it needs to deposit itself unnoticed among strangers: a trick essential to its survival. Truly it is the changeling of the animal world, as worthy of the title as the fairy babies who pass for mortals in the old folktales. For once this larva has invaded a litter of infant shrews, it comports itself like a regular member of that copious household. Its pudgy but tiny shape, pink flesh and downy fur (actually tubercles) mimic the attributes of the suckling mammal well enough that the shrew mother, more often than not, will accept the counterfeit, and allow it to feed with the others.

The milk of the shrew will sustain the worm (it is the only victual that can) until it senses the approach of metamorphosis. Before that hour comes, the larva must escape the brood, then find a cranny among the stones and fallen leaves where it may pupate. This brings us to its second ruse, for our chrysalid should become dull in texture and assume an earthen colour. If all has gone well, it should now be scarcely distinguishable from a pebble — a tiny hard morsel of stone, a source of neither meat nor interest to hungry parties that pass it by.

But our subject is thrice-deceptive, hence its name. The third subterfuge is plain to anyone who sees our triple-ruse hawk moth, now full-grown, land on its favorite resting place — the trunk of an elm — and immediately vanish, its cryptic brown wings a perfect forgery of the bark.

From: A. Burnleath Harthawick, Arthropods and Vermes of the Upper Plundtra. Cassell & Co., Limited, 1821: p. 117.