COLOURS AND FORMS OF INSECTS. 141 



superabundant production would be frustrated. We 

 have no doubt, indeed, that insectivorous animals can 

 instinctively detect their prey, in all the usual modes of 

 concealment, as acutely as the practised eye of a na- 

 turalist, who can with ease perceive what escapes the 

 observation of the inexperienced. When a woodpeck- 

 er is taught by nature to detect a wood- boring cater- 

 pillar, by the bark sounding hollow when tapped with 

 his bill, and when an ichneumon fly can detect a chry- 

 salis closely rolled up in a leaf,* we should be strongly 

 inclined to doubt that colour or form could afford very 

 effectual concealment from enemies, though we readily 

 grant that many probable instances of this have been 

 adduced. Of these instances it may be well to give 

 a few examples. 



The caterpillar of a nocturnal moth (Noctua algce, 

 FABR.) is said to assume the colour of the lichens 

 upon which it feeds, being gray when it feeds on a 

 gray one (Parmelia saxatilis, ACH.), and always yel- 

 low when it feeds on a yellow one (Cctraria juni- 

 perina, ACH.);| the change of colour being (it is 

 alleged) intended by Providence to conceal it from 

 its enemies, as it becomes difficult to distinguish it 

 from the lichens. The caterpillar of the coronet moth 

 (Jlcronycta Ligustri, OCHSENHEIM.), which feeds 

 upon the privet, is so exactly of the colour of the un- 

 derside of the leaf, to which it usually clings during 

 the day, that a person may have the leaf in his hand 

 without discovering the caterpillar ;J a circumstance 

 explained upon the same principle. This, indeed, is 

 no common circumstance, as many caterpillars 

 very nearly resemble the colour of the leaves upon 

 which they feed ; and the wonder rather is, that so 



* See { Insect Architecture, 5 p. 174-5. 



t Fabr. Vorlesung. in Kirby and Spence, ii, 220. 



j: Brahm, Insecten, in ibid, p. 221. 



