Forest entomology . ther in-sects are the elytraor wing-cases. Thesehave sometimes a very remarkable sculpturing, the use of which isunknown. In repose, these two elytra are very well fitted together : the junction line is knownas the suture. The wingsproper, which correspond tothe posterior pair of otherinsects, present a very vari-able structure, so far as thearrangements of nerves andcells are concerned. Thesize and general structureare compatible with thefolding up under the elytra(fig. 40). In some formsthey are considered apter-ous, but though in suchcases the wings are neverused, and th
Forest entomology . ther in-sects are the elytraor wing-cases. Thesehave sometimes a very remarkable sculpturing, the use of which isunknown. In repose, these two elytra are very well fitted together : the junction line is knownas the suture. The wingsproper, which correspond tothe posterior pair of otherinsects, present a very vari-able structure, so far as thearrangements of nerves andcells are concerned. Thesize and general structureare compatible with thefolding up under the elytra(fig. 40). In some formsthey are considered apter-ous, but though in suchcases the wings are neverused, and the elytra some-times soldered together, rudi-mentary wings may often befound. Throughout the respectivefamilies various modifica-tions of general anatomypresent themselves. In theRhynchoplwra or weevils,for instance, there is aprolongation of the mouthcalled a rostrum, which,as Canon Fowler remarks, is a true portion of the head, and inno sense a trunk. Classification.—^Notwithstanding the many works on Coleoptera,. Fig. 41. — Typical beetle: Pterostichus vulgaris, L.{mate); upper side. (From Fowlers British Coleop-tera. ) 1. Labium. 2. Labial palpus. 3. Maxilla. 4. Maxillary palpus. 5. Mandible. 6. Antenna. Front of head. 8. Supra-orbital setre. 9. Pronotum, ordinarily called thorax. 10. Anterior lateral pore. 11. Angular pore. 12. Scutellum. 13. Basal fold of elytra. 14. Scutellary stria. 15. Suture of elytra. 16. Sutural angle. 17. Tibia. 19. Spurs of tibia. 20. Tarsus. 21. Onychimn and claws. 22. Stigma. 23. Pygidium. COLEOPTERA. 41 we have no fixed system of classification or method of arrangingbeetles. In catalogues they are generally grouped into familiesaccording to the number of joints of the tarsi: thus those possessingfive joints to all the tarsi have been termed Pentamera ; those withfive joints to the front and middle legs, and only four to the hinder,Heteromera ; those with apparently only four to all the tarsi, Tetramera;and those with apparently onl
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