250 IN SECT A. 



lamellicorn beetles, exhibit considerable dimensions. These spines 

 are sometimes bifurcated or branched ; but, whatever their shape or 

 size they never grow from bulbs implanted in the cutis, but are 

 mere prolongations of the exterior layer of the integument. 



The hairs in their mode of growth appear to resemble those of 

 quadrupeds, inasmuch as they are secreted from roots embedded in 

 the substance of the cutis or true skin : they are fine horny cy- 

 linders, and frequently are found to be branched and divided like 

 the feathers of birds ; but the manner of their formation will be 

 more conveniently discussed hereafter. 



The wings of the Lepidoptera are covered with minute flat 

 scales of various shapes, and not unfrequently tinted with the most 

 beautiful colours ; such scales, nevertheless, are in reality only 

 flattened hairs, into which indeed they frequently degenerate by in- 

 sensible transitions, and, moreover, they grow from bulbs of pre- 

 cisely similar construction. The variety of colours exhibited by 

 the scales of a butterfly depends upon a film of pigment interposed 

 between the two plates of transparent epidermic matter forming 

 each ; but the gorgeous hues derived from this source must not be 

 confounded with the iridescent tints for which they are not un- 

 frequently remarkable, as these have a very different origin : the 

 surface of every scale, that with the changing light reflects 

 evanescent prismatic colours, is seen, when examined under a micro- 

 scope, to be marked with regular parallel striae of exquisite minute- 

 ness ; and such a surface, even when grossly imitated by human art, 

 has been found to give rise to the brilliant appearances exhibited 

 by polarized light. 



(292.) The muscular system of insects has always excited the 

 wonder and astonishment of the naturalist, in whatever point of view 

 he examines this part of their economy, whether he considers the 

 perfection of their movements, the inconceivable minuteness of 

 the parts moved, or the strength, persistence, or velocity of their 

 contractions. Insects are proverbially of small comparative dimen- 

 sions " minims of nature" 



" that wave their limber fans 

 For wings, and smallest lineaments exact, 

 In all the liveries decked of summer's pride j" 



their presence, indeed, around us, is only remarked as conferring 

 additional life and gaiety to the landscape ; and, except when by 

 some inordinate increase in their numbers they make up by their 

 multitude for their diminutive size, the ravages committed by them 



