344 Mr. A. R. Wallace on 



appearance of the yellow spot at the base of the lower wings be- 

 neath leads to P. agathon, which otherwise appears so different. 



(Pieris h'lppia, Bremer, Lep. Ost-Sibiriens, tab. iii. f. 1, from 

 East Siberia, is very near P. soracta, Moore.) 



Thyca, Wallengren. 



This genus is well distinguished by having only one subcostal 

 nervure given off before the end of the cell, the first being always 

 absent. The body is comparatively small, the antennas are gene- 

 rally long and slender, the wings ample, the uppers often much elon- 

 gated. The larvae are clothed with long hairs, and the pupse are 

 spined on the under surface. 



This group is preeminently a natural one. It consists of rather 

 large insects, which are adorned with more rich and variegated 

 hues than any other old-world Pierklce ; and, like so many other 

 richly-coloured insects, they are found only in the vast forests, 

 which, with few interruptions, spread continuously from the slopes 

 of the Himalayas through Malacca and the Malayan Islands to 

 North Australia and the Pacific. They all fly weakly and slowly, 

 yet they are by no means rare, since in almost every locality I 

 found some of the species very abundant in the forests, flying 

 lazily along near the ground, sometimes settling on a flower, but 

 more generally seeming to wander aimlessly through the pathless 

 recesses of the forest. It is probable, then, that they have some 

 special protection which renders swiftness of motion and the dis- 

 guise of sombre colours unnecessary, and this seems the more 

 probable when we find that some of them are the subjects of 

 mimicry, as already pointed out in the introduction, and under the 

 genus Prioneris. 



Thyca appears to be closely related to the American genus 

 Euterpe, since it not only agrees in many of its species having a 

 dark ground-colour, but hardly offers any constant structural 

 differences. 



I arrange the species under the following groups : — 



a. Pasithoe group. Lower wings marked with a red semicircle 



at their base beneath. 



b. Belladonna g\-ou\i. Lower wings with a basal yellow patch. 



c. BeUsama group. Lower wings with a red spot at the base 



beneath, between the costal and sub- 

 costal ncrvures. 



