Page:Jardine Naturalist's library Entomology.djvu/112

106 and the hinder section, to which the hind-legs and hind-wings are attached, is the metathorax. In apterous insects these divisions are the only ones distinctly determined, but in those provided with wings a more complex arrangement results from the muscular apparatus requisite to produce their movements.

In its greatest state of development, (which it attains among the coleoptera and orthoptera,) the prothorax (Manitrunk of Kirby,) forms that large, quadrate, rounded, or oblong piece intermediate between the head and abdomen, which, in popular and descriptive language, is simply called the thorax. Its surface is the pronotum of Burmeister, the thoracic shield of Kirby. Its forms are too diversified to be specified here; it commonly has an impressed line down the centre, at other times the centre rises into a longitudinal serrated ridge. The inferior plate is named the prosternum by Burmeister: (Antepectus, Kirby,) it is of more limited dimensions than the surface plate, and usually projects into a kind of angle beneath; the anterior legs are inserted, one on each side, towards the middle, and the prothoracic spiracle is commonly a little behind them. Viewed from above, the prothorax sometimes forms merely a narrow ring like a collar, and in certain tribes all traces of it disappear in the dorsal aspect, the head being apparently articulated directly with the mesothorax. The various changes of form which the prothorax, as well as the other primary divisions, undergoes in the different orders, together with its appendages, and the degree of development