424 COLEOPTERA. 



terior pair of wings (elytra) , often retain traces of the original 

 veins, consisting of three or four longitudinal lines. Their 

 office in flight seems to be to assist the hind wings in sustain- 

 ing the body, as but rarely when the insect is on the wing do 

 the elytra remain quiet on the back. The membranous hind 

 wings are provided with the usual number of principal veins, 

 but these are not subdivided into veinlets. The wing is long, 

 naiTOW and pointed, with the costal edge strong, being evi- 

 dently adapted for a swift and powerful flight. 



In the running species, such as many Carabidce, the 

 hind wings being useless, are aborted, and very rarely in some 

 tropical Lampyridce and Scarabceidce are both pairs of 

 wings wanting in both sexes, though, as in the Glow-worm 

 and some of its allies the females are apterous. The legs 

 are well developed, as the beetles are among the most power- 

 ful running insects. The coxae are large and of much use in 

 distinguishing the families. The trochantine is usually present 

 in the forelegs, but often absent in the middle pair ; the tro- 

 chanters, or second joint of the leg, is small, circular, ob- 

 liquely cut off, and the femur and tibia lying next beyond 

 are of varying form, correlated with the habits of thQ insect, 

 the hinder pair becoming oar-like in the swimming Dytiscidce 

 and some Hydrophilidce , while in m the Gyrinidce both 

 pairs of hind legs become broad and flat. The number of 

 tarsal joints varies from the normal number, five, to four and 

 three joints, the terminal joint as usual being two-clawed. 

 These claws are only known to be wanting in Phanaeus, a 

 Scarabseid, and the aberrant family Styl op idee. According 

 to the number of the tarsal joints the families of Coleoptera 

 have been grouped into the Pentamera (five-jointed), the Tet- 

 ramera (four-jointed), the Trimera (three-jointed), and Hete- 

 romera, which are four-jointed in the hind pair, while the first 

 and second pairs are five-jointed. 



The abdomen, usually partly concealed by the wings, is ses- 

 sile, its base broad ; in form it is usually somewhat flattened. 

 The tergal and sternal portion of each ring is connected 

 usually by the membranous pleura! piece, which represents 

 the epimera and episterna of the thorax, and on which the stig- 

 mata are situated. While in the other suborders the typical 



