. An introduction to zoology, with directions for practical work (invertebrates). IN SECT A : NEUROPTERA 317 opaque—the characteristic which has led to these forms being sometimes grouped in a special order, the Triduyptera. The nervature of the wings is peculiar in having very few trans- verse nervures (Fig. 240). The broad hind wings are folded fan- wise under the front wings when at rest, the latter being merely laid obliquely over the back and sides, as in the alder-flies. There is a well-marked metamorphosis with a quiescent pupal stage, which takes place below the water. The pupa, howeve
. An introduction to zoology, with directions for practical work (invertebrates). IN SECT A : NEUROPTERA 317 opaque—the characteristic which has led to these forms being sometimes grouped in a special order, the Triduyptera. The nervature of the wings is peculiar in having very few trans- verse nervures (Fig. 240). The broad hind wings are folded fan- wise under the front wings when at rest, the latter being merely laid obliquely over the back and sides, as in the alder-flies. There is a well-marked metamorphosis with a quiescent pupal stage, which takes place below the water. The pupa, however,. just before moult- ing the pupal skin, becomes active, and swims to the surface. The antennae of the imago are thread-like, and the mouth- parts are reduced, the mandibles being absent or very rudimentary, though present in the pupa (see p. 324).. Fio. 240.—Caddis-fly. Eggs. Life-history of a Caddis-fly. The rather moth-like, dull-coloured Caddis-flies are often to be seen on plants by the water side, or flying rather feebly close by (Plate III., /). The eggs are laid in the summer, in a mass surrounded by jelly. They are either dropped by the female at the water surface, or in some cases she is said actually to enter the water and deposit the mucilaginous egg- mass on some water-plant stem, or other object (Plate III., E). The egg-mass is sometimes in the form of a jelly-like rope, which may be an inch or more long, or it may be a ring, or simply a flat disc of jelly. The eggs, which are often greenish in colour, are clearly to be seen inside. The Larvae The larvae hatch out after two to three weeks, or Caddis- and at once begin to make for themselves little worms, protective cases out of any suitable material that may be at hand in the water. When the larva is full grown, its case has usually a characteristic appearance according to the species which has made it. One such case is shown in Fig. 242, P, with the caddis-worm projecting from one end. The larva under norma
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Keywords: ., bookcentury1900, bookdecade1910, bookpublisherlondo, bookyear1913
