INTRODUCTION. 
67 
of the genus Pieris are white ; Colias and Calli- 
dryas various shades of yellow, from the palest sul- 
phur-yellow to deep reddish-ochre. A rgynnis 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 
Euplcea, have this character in common, that the 
breast and head are always punctured with white. 
In Cetkosia, 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 
