220 A NATURALIST IN BORNEO 



by their obscure cryptic coloration, but cryptic colour- 

 ing is of no protective value if the insects possessing 

 it do not hide themselves as much as possible in 

 suitable situations ; and this is exactly what the two 

 species of Ypthima do not do. They expose them- 

 selves freely, fluttering with weak and uncertain flight 

 close to the ground, settling only for a few moments, 

 and then not in particularly obscure spots. We can- 

 not suppose that these butterflies are distasteful, for they 

 exhibit none of the characteristics of known distasteful 

 forms. Many more instances could be brought forward, 

 e.g. Melanitis ismene, Precis iphita, P. atlites, are all 

 cryptically coloured species, and yet expose them- 

 selves quite freely, and are excessively abundant. In 

 my opinion these species are abundant by virtue of 

 great fecundity, enabling them to maintain their 

 numbers in the face of a heavy destruction. This 

 is a mere suggestion, for in truth we are profoundly 

 ignorant of the reasons whereby one species may be 

 abundant and another, perhaps closely allied, extremely 

 rare. That the balance of forces regulating the abund- 

 ance or rarity of any species is liable to be upset at 

 any time is shown by the overwhelming numbers in 

 which a species may appear from time to time. 



One such instance came very forcibly under my 

 notice. One day at 2 p.m. [the date is not recorded] 

 there suddenly appeared at Kuching an enormous 

 swarm of the Nymphaline butterfly Cirrochroa bajadeta ? 

 For the space of fifteen minutes there poured over the 

 entire town countless numbers of the butterflies. All 

 were travelling in an east to west direction, and they 

 flew at a good pace. I am anxious not to exaggerate, 

 so will not say, like the Irishman, that the butterflies 



