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Show 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 beeu exceedingly difficult, if not impossible, to find any of sufficient size in the immediate neighbourhood of Kampong Aring. Hymenopus bicornis, 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 winch the 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 iu considerable numbers without being detected. This would have beeu perfectly true had the Mantis been in the habit of sitting still; but movement 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 iu holding its ow7n 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 iusect must either perish or alter both its structure and its habits immediately, a thing which no highly-specialized animal is likely to do rapidly. N o w 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 beeu 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, 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 tbe insects which live upon it. In lower Siam over a hundred varieties of |