. The biology of insects. Insects -- Biology. 58 THE BIOLOGY OF INSECTS and Grasshoppers), Plecoptera (Stone-flies), Isoptera (Ter- mites), the wings of the two pairs are uncoupled and each wing-bearing segment has its own set of thoracic muscles. But, on the other hand, in the great majority of highly organised flying insects of other orders there is some form of wing-coupHng apparatus, so that the fore and hind wing of each side move in unison, following the rhythmic changes of outline of the thorax due to the alternate con- traction of the sets of flight-muscles. Thus among the Fig.
. The biology of insects. Insects -- Biology. 58 THE BIOLOGY OF INSECTS and Grasshoppers), Plecoptera (Stone-flies), Isoptera (Ter- mites), the wings of the two pairs are uncoupled and each wing-bearing segment has its own set of thoracic muscles. But, on the other hand, in the great majority of highly organised flying insects of other orders there is some form of wing-coupHng apparatus, so that the fore and hind wing of each side move in unison, following the rhythmic changes of outline of the thorax due to the alternate con- traction of the sets of flight-muscles. Thus among the Fig. 20.—Right wings of Honey Bee {Apis), h, row of booklets on costa of hindwing which hold dorsal edge of forewing during flight. X 8. After Comstock and Needham and Snodgrass. wasps, and other insects of the order Hymenoptera a series of curved hook-like bristles along the front edge (costa) of the hindwing catch on the thickened hind-edge (dorsum) of the forewing (Fig. 20) ; it is easy to demonstrate this linkage by manipulating the wings of a large wasp or sawfly. In some of the Lacewing and Scorpion-fly groups (Neuroptera and Mecoptera), as R. J. Tillyard (1920) has pointed out, there is a lobe or process (jugum) at the hind- base of the forewing, and on the costa of the hindwing a corresponding humeral lobe bearing one or two stiff bristles (frenulum). The jugum is present also in many Trichoptera (Caddis-flies) and in a few Lepidoptera (Moths), though in. 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 Carpenter, George H. (George Herbert), 1865-1939. New York, The Macmillan Company
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Keywords: ., bookcentury1900, bookdecade1920, bookpublishernewyorkthemacmilla
