INSECTS AND ARACHNID A. 



225 



corrugation of the under membranous lamina alone; the upper or exposed 

 lamina being smooth, with the exception of slight undulations near the 

 pedicle; and the cross-markings being due to structure between the super- 

 posed membranes, probably a deposit on the interior surface of one or 

 both of them. 1 



623. Although the Poduridce and Lepismidcv now rank as distinct 

 Families, yet they approximate sufficiently in general organization, as 

 well as in habits, to justify the expectation that their scales would be 

 framed upon the same plan. The Podurida are found amidst the saw- 

 dust of wine-cellars, in garden tool-houses, or near decaying wood; and 

 derive their popular name of ' spring-tails ' from the possession by many 

 of them of a curious caudal appendage, by which they can leap like fleas. 

 This is particularly well developed in the species now designated Lepido- 

 cyrtus curvicollis, which furnishes what are ordinarily known as ( Podura '- 



FIG. 419. 



FIG. 420. 



Test-scales of Lepidocyrtus curvicollis: 

 A, large, strongly-marked scale: B, small 

 scale, more faintly marked. 



Ordinary scale of 

 Lepidocyrtus curvicollis. 



scales. "When full-grown and unrubbed," says Sir John Lubbock, 

 "this species is very beautiful, and reflects the most gorgeous metallic 

 tints." Its scales are of different sizes and of different degrees of strength 

 of marking (Fig. 419, A, B), and are therefore by no means of uniform 

 value as tests. The general appearance of their surface, under a power 

 not sufficient to resolve their markings, ia that of watered silk, light 

 and dark bands passing across it with wavy irregularity; but a well-cor- 

 rected Objective of very moderate angular aperture now suffices to resolve 

 every dark band into a row of distinct 'exclamation marks' (Plate II., 

 fig. 2). If, however, they are illuminated by oblique light from above 

 (the scales being placed under the objective without any cover, so as to 

 avoid the loss of light by reflection from its surface), the appearances 

 presented are those shown in fig. 4 when the markings are at right angles 



1 See Mr. Joseph Beck, in Sir J. Lubbock's " Monograph," p. 253. 

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