Packard.] INSECTS AS MIMICS. 271 



its back exactly like tlie leaf scars of the juniper, and the 

 entire worm concolorous throughout with the bark is a per- 

 fect imitation of the twig. 



Nearly every bush has its distinct kind of inch worm or 

 geometer, which resembles a broken branch or twig when 

 it is at rest and holds itself out stiff 'by its muscular 

 hind legs. Most caterpillars remain quiet by da^^ when 

 they need protection, and feed at night. The stick insect 

 (Fig. 209, from Tenney's Zoology) is so obviously a mimetic 

 form that we need only speculate how it came to differ from 

 its allied forms, unless the intermediate forms have become 

 extinct through the want of similar adaptation. This and 

 the celebrated leaf-insect are the two insects which first 

 come to mind when the subject of mimicry is mentioned. 

 The Phyllium is broad and flat, with leaf-like dilatations on 

 the legs, Avhile the broad wings are provided with a midrib 

 and vein exactly like a dried leaf. 



Other remarkable stick insects of the group of Phasmids 

 are figured by Professor Westwood in his "Tiiesaurus Euto- 

 mologicus Oxoniensis." Such as the Extatosoma bufonium 

 from Australia, Ileteropteryx Castehiandii from Tringany, 

 Malacca and Ceroys laciniatus from Nicaragua. They are 

 much alike in form, though inhabiting different quarters of 

 the globe, and are slender, with long legs, with flattened 

 tubercles and spiny expansions, resembling the young and 

 spiny twigs on which they possibly rest. 



The caterpillars of the leaf-rolling and Tineid moths 

 often live in rolled-up leaves, where they are protected 

 in a great measure from their enemies ; thougli the insec- 

 tivorous birds, attracted perliaps b}' the deformation they 

 cause in the foliage, feed ui)C)n them ; and their insect 

 parasites, particularly the minute chalcid flies, have the 

 requisite instinct to find them out and oviposit in their 

 bodies. No insects, hoAvevcr protected by these disguises, 

 arc ever thoroughly safe from the attacks of enemies cspe- 



15 



