The entomologist's text-book; an introduction to the natural history, structure, physiology and classification of insects, including the Crustacea and Arachnida / By J.O. Westwood.

  • John Obadiah Westwood
Date:
1838
Catalogue details

Licence: Public Domain Mark

Credit: The entomologist's text-book; an introduction to the natural history, structure, physiology and classification of insects, including the Crustacea and Arachnida / By J.O. Westwood. Source: Wellcome Collection.

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    DIPTERA. 41] ORDER XI.—DIPTERA. This order is distinguished by the presence of only a pair of membranous extended wings affixed to the centre of the sides of the thorax, and generally furnished near their in- sertion with a pair of short clubbed organs, termed halteres or balancers, respecting which, as analogically representing the posterior wings of the four-winged insects, entomologists are at variance. The mouth is provided with a sucker com- posed of from two to six scaly lancet-like pieces, and inclosed in a canal upon the upper surface of a fleshy proboscis, or covered by one or two inarticulated plates, which serve as a sheath (Hippobosca). The body is composed, as in the other six-legged insects, of three principal divisions, representing the head, thorax, and abdomen. The ocelli, when present, are generally three in number. The antennz exhibit vari- ous degrees of developement, from the exceeding length in the Macrocere and Megistocere to their scarcely visible size in the Hippobosce. In the Tipulide we find these organs composed of numerous articulations. In the Tabanide and a, Antenne of Tipula—s, of Tabanus—c, of Musca. Beride they are short, and the terminal articulations be- come almost indistinct, so that in the Muscide, &c., where they are very short, and appear to be composed only of three joints, having a terminal bristle, it is impossible not at once