LIFE-HISTORY. Owing to the difficulty of rear ing beetle larva, we know comparatively little of the life-history -of beetles. All undergo com plete metamorphosis. The eggs are laid in the situations where the economy of the species de mands that the grub should be born, in order to maintain itself—that is, upon or within ac cess of its food. Thus aquatic beetles lay their eggs in the water, leaf-eaters upon plants, wood bo•ers beneath the bark and in crevices of tim ber: the weevils upon tender seed-pods or young seeds, and so on. The scarabs (see DUNG-BEETLE and SCARAB) roll up their eggs in a ball of dry dung, and the burying beetles place theirs upon the carrion which is buried to await the hatch ing of the young. When the eggs are not laid so late as to be intended to remain dormant over winter, they batch quickly, and the larva begins at once to feed upon its intended fare.
The are commonly called 'grubs,' are usually whitish or of dull. inconspicuous hues, and ordinarily have three pairs of legs, one pair for each of the first three thoracic segments, which may vanish in older stages; hut grubs that live within their food may be legless. Grubs may possess traces of still other legs, a number of them having a pseudopod on the posterior end of the abdomen. Like adult beetles, grubs have
m a nd ilmlate mouth-parts, certain forms have channels in the mandibles through which liquid food is sucked. The larval state lasts for a number of years, which makes those species injurious to agriculture far more formidable than they might otherwise become.
Some beetles pupate in cocoons or eases, made of agglutinated hits of earth and wood. Those larva- that bore in wood go into the pupa stage in their burrows. Some forms pupate in the ground. others on the surface of the ground; while still others, such as the ladybird, sus pend themselves to objects above ground by the posterior ends of the body. Several pupate in the last larval skin. The pupal state of the majority of beetles lasts only two or three weeks, but in some cases it lasts several years. On account of the hardness of the exoskeleton, bee tles retain their shape well when dried, and hence collections of them are made with more ease than is possible in other departments of entomology, and adult beetles have been studied more than any other order of insects.