METAZOA INSECTA. 437 



large and, excepting the small mesothoracic scutellum 

 between the bases of the wing covers, is the only part of 

 the thoracic region seen from above. It forms with the 

 head a wedge-shaped portion of the body of advantage 

 to the insect when digging its way through the earth. 



When the elytra and wings are removed the small 

 mesothorax (fig. 4, ms) and the large metathorax (fig. 4, 

 mt) are seen. The junction of the thorax and abdomen 

 is broad like that of most of the types so far described. 



The antennae of the Scarabaeidae, the family to which 

 the May beetle belongs, are leaf-like or lamellate at the 

 end and hence the name .Lamellicorns often given to the 

 family. The antennae are usually tucked away under 

 the eyes and are extended only when needed. 



The mouth parts are of the biting type and are similar 

 to those of the Orthoptera. The six legs are adapted 

 pre-eminently for running. The wing covers or elytra are 

 characteristic organs giving the name of Coleoptera, mean- 

 ing sheath and wing, to the order. These elytra are 

 usually considered as the anterior pair of wings which 

 have become horny, but in which, according to Dimmock, 1 

 the remnants of veins can often be seen. According to 

 Comstock, 2 their structure " resembles that of the body 

 wall rather than that of wings, and in some beetles (e. g. 

 Dytiscus) rudiments [remnants] of the fore wings exist 

 beneath the elytra." The wing covers are of little use in 

 flight and hence the small size of the mesothorax which 

 bears them ; on the other hand, the wings are useful fly- 

 ing organs and the metathorax is consequently large and 

 strong. 



There is no external ovipositor and the abdomen of the 

 male and female are alike, excepting that in the former 

 the ventral side of the seventh segment has a transverse 

 ridge. Each of the first seven abdominal segments has a 



1 Stand. Nat. Hist., I, 1885. 



2 Manual for the Study of Insects, 1895, p. 494. 



