. Bulletin of the Department of Agriculture. Agriculture. THE WESTERN GRASS-STEM SAWFLY. 11 not yet visible. Over night, at the close of the fifth day, the jaws turn brown and the eye spots appear and darken. Usually, after the fourth day, the muscular system of the larva is in almost con- stant motion, sliifting and adjusting, with the heart pulsating and the muscles moving, all clearly to be seen through the transparent membrane that serves as the shell. The activity of the larva within the sac increases during the sixth day, and either on this day or the seventh it escapes from its con
. Bulletin of the Department of Agriculture. Agriculture. THE WESTERN GRASS-STEM SAWFLY. 11 not yet visible. Over night, at the close of the fifth day, the jaws turn brown and the eye spots appear and darken. Usually, after the fourth day, the muscular system of the larva is in almost con- stant motion, sliifting and adjusting, with the heart pulsating and the muscles moving, all clearly to be seen through the transparent membrane that serves as the shell. The activity of the larva within the sac increases during the sixth day, and either on this day or the seventh it escapes from its confine- ment by a series of convulsive movements that rupture the delicate shell and set it free. After the first day the egg changes shape, becomes intumescent, generally loses its crescentic shape entirely, and grows oval or reni- form in outline. THE LARVA When it escapes from the egg the larva ffig. 6) possesses a very large head armed with a pair of powerful biting jaws, a weak, slender body, and a most vigorous appetite. It is very active from the start and begins almost at once to feed upon the living parenchymatous tissue by which it is surrounded in the inte- rior of the stem, excavating for itself a threadlike gallery both above arid below the spot where the egg formerly lay. The larva is at first nearly transparent and colorless until it becomes filled with the tissue on which it exists. The body segments are strongly and clearly marked from the time the larva leaves the egg. The jaws are brown, three or four Fig. 6.—western grass-stem sawfly: . , 1,1 • , I'll 11 11 Newly-hatched larva. Greatly pointed, the points chisel-shaped, beveleci enlarged. on the inside edge. The brown face plate is filled with crossed bands of striated muscular fiber that actuate the powerful jaws which form the most important item of the domestic economy of the young Cephus. The caudal horn, by means of wliich the larva moves up and down in its gallery, is also brown and is armed, even in
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