. The Cambridge natural history. Zoology. POLYMORPHA—WHIRLIGIG-BEETLES 215 are five ventral segments visible along the middle, six at the sides, as in the families of Adephaga generally. There is said to be a great difference in the nervous systems of Carabidae and Paussidae, but so little is known on this point that we cannot judge whether it is really of importance. Fam. 11. Gyrinidae {Whirligig leetles).—Antennae verij short; four eyes; middle and hind legs forming short hroad 'paddles ; abdomen ivith six segments visible along the middle, seven (dong each side. These Insects are known to a
. The Cambridge natural history. Zoology. POLYMORPHA—WHIRLIGIG-BEETLES 215 are five ventral segments visible along the middle, six at the sides, as in the families of Adephaga generally. There is said to be a great difference in the nervous systems of Carabidae and Paussidae, but so little is known on this point that we cannot judge whether it is really of importance. Fam. 11. Gyrinidae {Whirligig leetles).—Antennae verij short; four eyes; middle and hind legs forming short hroad 'paddles ; abdomen ivith six segments visible along the middle, seven (dong each side. These Insects are known to all from their habit of floating lightly on the surface of water, and performing graceful complex curves round one another without colliding ; sometimes they may be met with in great congregations. They are admirably con- structed for this mode of life, which is com- paratively rare in the Insect world; the Hydrometridae amongst the bugs, and a small number of different kinds of Diptera, being the only other Insects that are devoted to a life on the surface of the waters. Of all these, Gyrinidae are in their construction the most adapted for such a career. They are able to dive to escape danger, and they then carry with them a small supply of air, but do not stay long beneath the surface. Their two hind pairs of legs are beautifully constructed as paddles, expanding mechanically when moved in the backward direction, and collapsing into an extremely small space directly the resistance they meet with is in the other direction. The front legs of these Insects are articulated to the thorax in a peculiar direction so that their soles do not look. Fig. 99.—A, Larva of Gyrinus (after Schiddte); B, under side of Gyrinus sp. (after Ganglbauer), 1, Prosternum ; 2, anterior coxal cavity ; 3. meso- thoracic episternum ; 4, mesoepimeron ; 5, meso- sterniim ; 6, metathoracic episternum ; 7, middle coxal cavity ; 8, metasternum ; 9, hind coxa ; 10, ventral segments. [—The first ven
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
