268 COMMON BRITISH MOTHS 



CHAPTEE XX 

 GEOMETRY 



WE have already referred (page 28) to caterpillars that walk by a 

 series of strides, alternately looping and extending their long and 

 slender bodies. It is this peculiar characteristic of the larvee of 

 the present division that suggested the name Geometrce a term 

 that signifies ' earth-measurers,' for they appear to measure the 

 ground over which they travel in terms of their own length. TVe 

 have also dealt with the peculiarities of structure in the case of 

 these caterpillars peculiarities which adapt them to this mode of 

 progression ; and we have now to make a selection from the various 

 families of this important division for a more detailed description. 

 The Geometrce include nearly three hundred species and six- 

 teen families. The moths have slender bodies and full wings, and 

 generally rest with the latter outspread. A few, however, repose 

 w r ith wings erect like the butterflies, and a small number conceal 

 their hind wings after the manner of the Noctuce. 



Family UROPTERYGHXE 

 The Swalloiv Tail (Uropteryx sambucaria) 



Our first family Uropterygidce has only one British represen- 

 tative, and that is the well-known Swallow Tail, so common in gar- 

 dens and among hedgerows in the south of England. This species 

 is shown on Plate XII (fig. 2), and the insect is so readily identified 

 by the conspicuous ' tails * on the hind wings that no written de- 

 scription will be necessary. 



The caterpillar is a most peculiar and interesting creature. Its 

 colour is very variable, being either brown, olive, ochreous, or red- 

 dish ; and it is notched or humped in such a manner that it exactly 

 resembles a twig. This strange imitation is rendered still more re- 



