Their food was the meat they killed in the chase, or seeds and roots, grubs or reptiles.
The vegetable-feeders attack leaves, herbaceous or woody stems and roots; frequently different parts of a plant are attacked in the two active stages of the life-history; the cockchafers, for example, eating leaves, and their grubs gnawing roots.
Stridulating organs among beetle-larvae have been noted, especially in the wood-feeding grub of the stag-beetles (Lucanidae) and their allies the Passalidae, and in the dung-eating grubs of the dor-beetles (Geotrupes), which belong to the chafer family (Scarabaeidae).
It has been suggested that the power of stridulation would be advantageous to wood-boring grubs, the sound warning each of the position of its neighbour, so that adjacent burrowers may not get in each other's way.
Beetles and larvae are frequently carnivorous in habit, hunting for small insects under stones, or pursuing the soft-skinned grubs of beetles and flies that bore in woody stems or succulent roots.
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