The bees seem to prefer the mengalis tree, which has so many angles and hollow places about its trunk that to build the comb is an easy matter. Not infrequently there may be fifty or more swarms in a single tree. When a bee-tree is to be robbed, great piles of a certain plant or weed are collected and put in such a position that the smoke will be carried against the nesting-places of the swarms. The piles are then fired. The smoke neither kills the bees nor does it drive them off; it merely stupefies them. When the humming of the bees is hushed, comb and honey are easily removed. A considerable part of the wax is exported, but thousands of tons are wasted. Hunting in the forests of Borneo has its unpleasant features, for the leeches are almost as numerous as the leaves of the trees. They are big, fat, ugly-looking slugs, but they can stretch their bodies into a small, thin form. When waiting for a victim they lengthen and sway their threadlike bodies to and fro, ready to launch out at the first opportunity. So gently do they commence their work that the pricking sensation is felt only when they are gorged with blood and begin to loosen their hold. The gathering of edible birds' nests, built by a kind of swallow, is quite an industry, and is confined to the rocky-cliff sections of certain parts of the coast where cover abounds. This species of swallow is smaller than the common swallow and builds its nest either in the dark limestone caverns or in the crevices and nooks of the overhanging cliffs. The chief material used in constructing the nest is a glutinous saliva produced by the bird itself. The Chinese are very fond of the nests, and Chinese merchants buy most of them. The roofs of some of the caves frequented by these swallows are several hundred feet above their floors, and to reach the nests, scattered over the curved roofs and sides, it is necessary to construct ladders and stages. These are made out of rattan and bamboo and are fastened by pegs driven into the limestone walls. Crawling up on these slender supports with a candle and forked bamboo pole, the native proceeds to detach the nests, which he passes to a companion below. When the nests are built in caves and crevices, near the top of cliffs, a swinging ladder is dropped from above. There are two kinds of nests, the clear yellowish-white ones, and the dark ones. The former bring a price as high as twelve dollars per pound; the latter only one-tenth as much. The best nests are found in the darkest caves. Bird-nest gathering is a perilous calling, and serious accidents are not infrequent. The nests are gathered two or three times a year.