. E PREGIUDIZIEVOLE insetti utili; introduzione allo studio di entomologia economica. Insetti; insetti utili; pesti di insetto. Fig. 30 Rapa-flea. stato 40 e pregiudizievole insetti utili i quattro giunti di Tarso indicano una sezione di Coleotteri noto come tetramera, che sono anche chiamati Phytophaga, dal loro gusto per il cibo vegetale. Chiudere examina- - zione mostra che in realtà esistono cinque articolazioni del tarso, ma che la quarta è ridotto a un retaggio di nessun uso pratico. I coleotteri fitofagi sono divisibili in tre famihes :-(i) Semi-mangiatori (Bruchidse), spesso confuso con il curculione;

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. Injurious and useful insects; an introduction to the study of economic entomology. Insects; Beneficial insects; Insect pests. Fig. 30 Turnip-flea. been 40 INJURIOUS AND USEFUL INSECTS The four joints of the tarsus indicate a section of Coleoptera known as Tetramera, which are also called Phytophaga, from their taste for vegetable food. Close examina- - tion shows that there are really five joints in the tarsus, but that the fourth is reduced to a vestige of no practical use. The phytophagous beetles are divisible into three famihes :—(i) Seed-eaters (Bruchidse), often confused with weevils; the so-called pea-weevil is an example; (2) the Leaf-eaters (Chrysomelidae), to which the flea-beetle be- longs ; and (3) the Longicorns or wood-eaters (Cerambycidae), named Longicorns from their long feelers, which often exceed the body in length. The flea-beetle feeds on all Cruciferous 1. plants, whether wild or cultivated, and is often found in places where turnips have grown. Large crops of turnips give it, of course, facilities for food and increase, which do not exist elsewhere. This beetle is active throughout the warm season, and produces several broods in close succession ; in winter it seeks shelter, and is rarely seen. The eggs are laid singly on the under side of leaves. The larva which issues from the egg is small and of pale yellow colour. It has a dark-coloured head, and three pairs of rather stumpy legs; the end of the abdo- men bends down and forms a sup- port. It is a leaf- miner, burrowing in the thickness of the leaf, eating up the green sub- stance, and leaving a sinuous discoloured track or burrow, where only the dead cuticle is to be found. The habit of leaf-mining is by no means restricted to this particular insect.. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.. Miall, Louis Comp