. An introduction to zoology, with directions for practical work (invertebrates). CHAP. XVII INSECT A: COLEOPTERA 243 a complete and great metamorphosis. The larva is some- times a legless grub, but often there are three pairs of small thoracic legs; the pupa is soft, with no hard protective pupal case; the organs of the imago show clearly through the thin pupal skin. This order is an enormous one numerically. It is reckoned that about 150,000 species are already known, and this number is constantly being added to \ a little over one-fiftieth of these are British. On the whole,beetles are not
. An introduction to zoology, with directions for practical work (invertebrates). CHAP. XVII INSECT A: COLEOPTERA 243 a complete and great metamorphosis. The larva is some- times a legless grub, but often there are three pairs of small thoracic legs; the pupa is soft, with no hard protective pupal case; the organs of the imago show clearly through the thin pupal skin. This order is an enormous one numerically. It is reckoned that about 150,000 species are already known, and this number is constantly being added to \ a little over one-fiftieth of these are British. On the whole,beetles are not such good fliers as most insects; indeed many of them use their wings but rarely, living mostly close to the ground where vegetation is dense and food plenti- ful. In some of these ground beetles the membranous wings are mere rudiments. A good many British forms are aquatic, and since the life-history of these is usually more easy to follow than that of the land forms, one of them will now be taken as the type for detailed study. Sub-order 1: Adephaga (Beetles with Thread-like Antennae). These forms are sometimes also known as the " Carnivora,'' on account of the nature of their food. The larvae as well as the adult beetles are excep- tionally active and predaceous. Tyye,: The Carnivorous Water Beetle (Dyticus marginalis). Byticus marginalis is a large handsome beetle, very common in ponds, often seen at the sur- face as it tilts the tip of its abdomen out of the water to take in a fresh supply of air. If alarmed, it dives very rapidly down to the bottom, soon, however, floating up again, for its body is lighter than the water, and so it is unable to remain below except by active movement or by clinging to some support. This beetle can be very easily kept in. Fig. 169.—The Carnivorous Water Beetle (Dyticus marginalia). (A, Antennae ; d, disc on front leg, characteristic of the Please note that these images are extracted from scanned page images that may have been
Size: 1434px × 1743px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, bookpublisherlondo, bookyear1913
