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 . hese tubes at first contain blood, whichhas been observed to circulate through them, and since the heart canbe most easily injected through them, they may more properly becalled veins than nervures. The shape and venation of the wingsafford excellent ordinal as well as family and generic characters,while they also enable the systematist to exactly locate the spotsand other markings of the wings
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 . hese tubes at first contain blood, whichhas been observed to circulate through them, and since the heart canbe most easily injected through them, they may more properly becalled veins than nervures. The shape and venation of the wingsafford excellent ordinal as well as family and generic characters,while they also enable the systematist to exactly locate the spotsand other markings of the wings. The spaces enclosed by the veinsand their cross-branches are called cells, and their shape often affordsvaluable generic and specific characters. The structure of a complete vein is described by Spuler. In across-section of a noctuid moth (TripJiwna pronuba, Fig. 136) thechitinous walls are seen to consist of two layers, an outer (u) andinner (c), the latter of which takes a stain and lies next to thehypodermis (hy). In the cavity of the vein is the trachea (tr~),which shows more or less distinctly the so-called spiral thread;within the cavity are also Sempers rib (r) and blood-corpuscles hy V. FIG. 136.—Cross-section of \\ing Fio. 137.— Cross-section of wing of Pirns : .«, insertionsof Pronuba. — Atu-r Spuler. of scales.—After Spuler. (be), which proves that the blood circulates in the veins of the com-pletely formed wing, though this does not apply to all Lepidopterawith hard mature wings. We have been able to observe the samestructure in sections of the wing of Zygaena. 122 TEXT-BOOK OF ENTOMOLOGY A cross-section of a vein of Picris brassicce shows that the largetrachea is first formed, and that it extends along the track betweenthe protoplasmic threads connecting the two hypodermal layers. The main tracheae throw off on both sides a number of secondarybranches showing at their end a cell with an iiitracellnlar trachealstructure; these accessory tracheae afterward
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishe, booksubjectinsects
