. Injurious and useful insects; an introduction to the study of economic entomology. Insects; Beneficial insects; Insect pests. 174 INJURIOUS AND USEFUL INSECTS sometimes resting long in this position. When the feet are sufficiently hard to hold firmly, the fly erects itself again, grasps its support, and bends the abdomen vigorously until it becomes free. During the casting of the larval skin the linings of the great air-tubes are withdrawn from the thoracic spiracles, and left adhering to the empty integument as white threads. When the fly is disengaged, it is flabby and incapable of active
. Injurious and useful insects; an introduction to the study of economic entomology. Insects; Beneficial insects; Insect pests. 174 INJURIOUS AND USEFUL INSECTS sometimes resting long in this position. When the feet are sufficiently hard to hold firmly, the fly erects itself again, grasps its support, and bends the abdomen vigorously until it becomes free. During the casting of the larval skin the linings of the great air-tubes are withdrawn from the thoracic spiracles, and left adhering to the empty integument as white threads. When the fly is disengaged, it is flabby and incapable of active movement. The abdomen has not yet gained its full length, while the wings are still soft and crumpled. They slowly unfold and increase in firmness. During this expansion it can be seen with a lens that a clear fluid, no doubt the blood, is. Fig. 92.—Adult dragon-fly (Libellula). After Charpentier. injected into the veins of the wing. In a quarter of an hour the wings may be fully expanded, but they are not yet firm enough to support the body in the air. Two or three hours often elapse before the fly can trust its weight to them. During the expansion and hardening of the wings the colours of the body become more deep and vivid. The rapidity with which the tints develop, the rapidity with which they are lost after death, and the fact that little pigment can be extracted from a dragon-fly by alcohol and other solvents, suggest that the coloration is largely due to surface markings which modify the reflection of light. In insects, as in many birds and a very few mammals, bright and varied patterns may be got by inter- ference colours with little or no use of pigment. The fly is magnificently equipped for flight. Each of the. 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 Miall, Louis Compton, 1842-. London, G
Size: 1982px × 1260px
Photo credit: © Central Historic Books / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, booksubjectinsects, bookyear1902
