INTRODUCTION. 67 



of the genus Pieris are white; Colias and Callv> 

 dryas various shades of yellow, from the palest sul- 

 phur-yellow to deep reddish-ochre. Argynnis is 

 almost invariably fulvous or reddish brown, varie- 

 gated with numerous undulating black lines or spots; 

 the under side more or less ornamented with silvery 

 streaks and spots. In the species of the European 

 genus Thais, the wings are spotted or chequered 

 with black and red. The prevailing colour in the 

 genus Argus is azure-blue. Danais, Idcea, and 

 Euploea, have this character in tommon, that the 

 breast and head are always punctured with white. 

 In Cethosia, hieroglyphical markings cover the under 

 side of the wings in such a manner as is observable 

 in no other genus. 



Many of the caterpillars of exotic butterflies offer 

 peculiarities in their forms and appendages, of which 

 we find no prototype in the kinds occurring in Bri- 

 tain. In the place of spines, some have the body 

 thickly covered with long fleshy prominences, of a 

 corneous consistency at the tip, and probably serv- 

 ing as a means of defence. In others, spines of 

 singular conformation and formidable size are thick- 

 ly stuck over the whole surface, making it resemble 

 a miniature forest. A few are provided with a long 

 anal horn, resembling that which is so conspicuous 

 in the caterpillars of the Sphinges. If Madam 

 Merian s delineation of the larva of Urania Leilus 

 be correct (which there is now reason to believe is 

 the case), it bears many slender spines, as long as 

 the whole body, and as stiff as iron wire. Another 



