40 



FOREST ENTOMOLOGY. 



Fig. 40. True icings of beetle. 



the tarsus, into four divisions viz., Trimera, Tetramera, Heteromera, 

 and Pentamera. This division is, of course, more or less arbitrary. 



The wings of beetles 

 are rather peculiar, as 

 what corresponds with 

 the wings of other in- 

 sects are the elytra 

 a, folded ; 6, unfolded. or w ing-cases. These 



have sometimes a very remarkable sculpturing, the use of which is 

 unknown. In repose, these two elytra are very well fitted together : 



the junction line is known 

 as the suture. The wings 

 proper, which correspond to 

 the posterior pair of other 

 insects, present a very vari- 

 able structure, so far as the 

 arrangements of nerves and 

 cells are concerned. The 

 size and general structure 

 are compatible with the 

 folding up under the elytra 

 (tig. 40). In some forms 

 they are considered apter- 

 ous, but though in such 

 cases the wings are never 

 used, and the elytra some- 

 times soldered together, rudi- 

 mentary wings may often be 

 found. 



Throughout the respective 

 families various modifica- 

 tions of general anatomy 

 present themselves. In the 

 Rhyncliopliora or weevils, 

 for instance, there is a 

 prolongation of the mouth 

 called a rostrum, which, 

 as Canon Fowler remarks, is a true portion of the head, and in 

 no sense a trunk. 



Classification. Notwithstanding the many works on Coleoptera, 



Fig. 41. Typical beetle : Pterosticlms vulgaris, L. 

 {male); upper side. (From Fowler's ' British Coleop- 

 tera. ') 



1. Labrum. 



2. Labial palpus. 



3. Maxilla. 



4. Maxillary palpus. 



5. Mandible. 



6. Antenna. 



7. Front of head. 



8. Supra-orbital setse. 



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. Femur. 

 IS. Tibia. 



19. Spurs of tibia. 



20. Tarsus. 



21. Onychium and claws. 



22. Stigma. 



23. Pveidium. 



