Page:The Zoologist, 4th series, vol 3 (1899).djvu/478

448 at night. This is true of most ground-beetles, many Crickets, Cockroaches, Ants, &c. Many of these insects hide away in the daytime, so that no protective colours are then needed. But many insects that are exposed both during the day and at night have acquired green or yellowish colours that are protective at all times, when living among foliage. Green-grasshoppers, Katydids, &c, are examples."

Sometimes we find varied or almost contradictory suggestions, as has been applied to the resemblance of Tree-Shrews to Squirrels. Lydekker considers this may have been originally due to the extreme agility of the latter animals insuring them from pursuit by other creatures, as being a useless task. Hence it would clearly be an advantage for a slower animal to be mistaken for a Squirrel. Wallace suggests that the resemblance is probably due to the Squirrels being harmless creatures which cannot alarm the insects around them by their movements, so that the Insectivora which resemble them easily capture their food. Another protective quality possessed by Squirrels has been conjectured by Poulton as existing in its large bushy tail: "An enemy in pursuit would be liable to get only a mouthful of fur." Ridley, in commenting on this proposed mimicry, is much more cautious: "If this resemblance is to be reckoned an example of mimicry, it is not easy to decide whether it is the Tupaia which mimics the Squirrel, or the Squirrel the Tupaia. Possibly the resemblance is accidental, both animals having taken on the most inconspicuous colouring, and the most suitable form for their environment." Mr. Oldfield Thomas considers that the resemblance between the Bassaricyon, a Raccoon-like type of animal (known at present only by a single skull from Costa Rica and a skin from Ecuador) to the Kinkajou (Cercoleptes caudivolvulus), a well-known Raccoon inhabiting Central America and Northern Brazil, is a case of true mimicry, although he is unable to