A text-book of entomology, including the anatomy, physiology, embryology and metamorphoses of insects, for use in agricultural and technical schools and colleges as well as by the working entomologist . 154 TEXT-BOOK OF ENTOMOLOGY of the wing-membrane, which is very extensive and complicated, and thereforeindicates the performance of an important function, perhaps of a kind ofbalancing sense, and also that these same insect wings, with their delicatemembrane, are very easily affected by different outside agents, as, for instance,warmth, currents of air, etc. Usually in their inactive or passiv
A text-book of entomology, including the anatomy, physiology, embryology and metamorphoses of insects, for use in agricultural and technical schools and colleges as well as by the working entomologist . 154 TEXT-BOOK OF ENTOMOLOGY of the wing-membrane, which is very extensive and complicated, and thereforeindicates the performance of an important function, perhaps of a kind ofbalancing sense, and also that these same insect wings, with their delicatemembrane, are very easily affected by different outside agents, as, for instance,warmth, currents of air, etc. Usually in their inactive or passive state the wings are held offhorizontally from the body during flight, and are laid upon the backagain when the insect alights ; but an exception occurs in mostbutterflies and Neuroptera, among which the wing-joint allows onlyone movement round the oblique and long axis of the wings. From. FIG. 169. — Anterior part of a Cicada for demonstrating the mechanism of the articulation of thefore wing: a, articular head ; ?<, articular pan, frog, or cotyla; ff, elastic band ; c, cl, (, system ofelastic rods ; t\, /3, 1st and 2d abdominal segments. Iff, hind wings. — After Graber. this cause, too, the insects just mentioned can unfold their wingssuddenly. The transition of the wings from the active to the resting condi-tion seems to be by way of a purely passive process, which, there-fore, usually gives no trouble to the insect. The wing beingextended by the tractive power of the muscles, flies back, when thisceases, to its former or resting posture by means of its natural elas-ticity, like a spiral spring disturbed from its balance. The structureof this spring joint is very different, however. It usually consists (Fig. 109) of two parts. The wing can move itself up anddown in a vertical plane by means of the forward joint, and at the same time canrotate somewhat round it
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishe, booksubjectinsects
