. Injurious and useful insects; an introduction to the study of economic entomology. Insects; Beneficial insects; Insect pests. A CARNIVOROUS WATER-BEETLE 35 forms a large flattened bubble. From this bubble air can be drawn into the body by a series of small spiracles which lie along the back. The female of the Dytiscus marginalis lays her eggs in March or April upon aquatic plants, making a deep incision for each egg with her ovipositor. In about three weeks the larva hatches out. It grows fast, and attains its full size in four or five weieks, being then about two inches lohg. The figure sho
. Injurious and useful insects; an introduction to the study of economic entomology. Insects; Beneficial insects; Insect pests. A CARNIVOROUS WATER-BEETLE 35 forms a large flattened bubble. From this bubble air can be drawn into the body by a series of small spiracles which lie along the back. The female of the Dytiscus marginalis lays her eggs in March or April upon aquatic plants, making a deep incision for each egg with her ovipositor. In about three weeks the larva hatches out. It grows fast, and attains its full size in four or five weieks, being then about two inches lohg. The figure shows the shape of the larva. We remark its rather lohg, fringed legs,-the fringed hinder segments, and the pair of fringed appendages borne by the last seg- ment of all. The legs and tail are both effective in swimming, but the tail is less important for swimming than for breathing. The larva is lighter than water, and can only remain below by grasping solid ob- jects. When it lets go, it rises to the surface, tail first. The water rolls off the hairy appendages in a moment, and then air can be sucked in by two spiracles, which open on the tip of the tail, and lead into the great longitudinal air-tubes. The action of the hairs can be explained by well-' known physical principles, but we must not stay to discuss the point here. There is one curiosity of structure about the mouth-parts of the larva which we must not pass over. Whoever examines the larval head with a pocket-lens will be sure to notice the long, sickle-shaped mandibles. It was pointed out by Swammerdam, as long ago as the seventeenth century, that these cruel weapons are hollow, and that when the larva preys upon a red-blooded victim, the blood can be seen to flow. Fig. 24.—Larva of 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 Mial
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectinsects, bookyear1902
