1900.] INSECTS OF THE " SKEAT EXPEDITION." 847 



the light ; and I am sorry that I did not experiment with other 

 flowers than those among which it was found. It would have been 

 exceedingly difficult, if not impossible, to find any of sufficient size 

 in the immediate neighbourhood of Kampong Aring. 



Hymenopus bicomis, the only representative of its genus, is 

 an insect which has a fairly wide distribution, being found in 

 Sikkim, Java, and Sarawak ; but in none of these localities does 

 it appear to be at all common ; in Kelautan it is exceedingly rare. 

 During the six weeks which 1he expedition spent at Aring, only 

 one specimen was seen, though every clearing in the district was 

 full of the blossoms of the Sendudok. It may be said that an 

 animal so well able to hide itself might easily exist in considerable 

 numbers without being detected. This would have been perfectly 

 true had the Mantis been in the habit of sitting still ; but move- 

 ment in an apparent flower is just as attractive to a biologist 

 as it is to a lizard. After the first specimen had been captured, 

 hundreds of bushes were examined with the very greatest care by 

 three zoologists and a botanist, but no Hymenopus was found. 

 Granted that the insect is as highly specialized in instinct as it 

 is in form— and I think there can be little doubt that this is 

 the case — it is not difficult to suggest an explanation of its rarity. 

 It is an animal which, for some reason, has had the greatest 

 difficulty in holding its own in past ages, and it has been driven 

 in the course of its struggle for existence to the extremes of 

 specialization. It has become so highly specialized, in fact, that it 

 has condemned itself, as it were, to a single and very limited 

 environment ; and should that environment be changed, even to 

 a slight extent, by external circumstances, the insect must either 

 perish or alter both its structure and its habits immediately, a 

 thing which no highly-specialized animal is likely to do rapidly. 

 Now in the Malay Peninsula the conditions of life are always 

 undergoing small changes that are apparent even to a traveller 

 hastening through the country ; there must be many that years of 

 research could not reveal. Suppose that the district of Aring 

 were decimated by the small-pox, as many a Malayan district has 

 been, and that the inhabitants who survived fled over into Pahang 

 with their buffaloes, in a few years the jungle would kill off all 

 the Sendudok bushes in the neighbourhood, for the plant can only 

 exist in a clearing. In olden times, before the advent of the 

 Malays into the Peninsula, the Sendudok must have been a rare 

 plant in Kelantan, as neither the Sakais nor any of the other 

 aboriginal tribes make clearings or keep cattle. The extremely 

 local nature of the fruiting-season of various semi-cultivated trees, 



J s 



such as the Mangosteen (Garcinia mangostana), must have some 

 influence on the insects of the different districts, and seems to 

 depend not so much on local variations of climate as on the 

 different varieties of the trees that are popular in the different 

 villages. One would like to know whether the variations of a 

 fruit of such ancient cultivation as the banana affect the insects 

 which live upon it. In lower Siam over a hundred varieties of 



