424 ARTHROPODA 



wings. The anterior pair, separated at the base by a scutellum, are hard 

 elvlra not fitted for flight, and from these comes the name Coleoptera, 

 sheath wings. Under the elytra are protected the delicate much folded 

 hinder wings, the organs of flight. Since the second and third thoracic 

 rings and those of the abdomen are covered by the elytra, these are soft 

 above. Externally the relations of the elytra cause a regional division 

 peculiar to the beetles (fig. 471): head, prothorax, and a third division 

 composed of meso- and metathorax plus abdomen covered by the elytra.- 



The numerous species of beetles over 100,000 described are divided into 

 normal forms and Rhynchophora, the normal forms being subdivided upon 

 characters derived from the tarsi as follows: 



Sub Order I. PENTAMERA. Tarsus five-jointed, the last club-shaped 

 and bearing the claws; the other four are short and somewhat heart-shaped 

 (fig. 472, a). This largest sub order contains the tiger beetles (CICINDELID.E), 

 the predaceous CARABID.E (fig. 471); water beetles, HYDROPHILHX*: and 

 DYTISCID.E; LAMELLICORNIA or SCARABEID^:, represented by the 'June bugs,' 

 Melolontha*; fire flies, LAMPYRID.E; rove beetles, STAPHYLINID.E, etc. Sub 

 Order II. HETEROMERA. First and second legs pentam- 

 crous, third apparently four-jointed; few species; 'oil bottles' 

 (MELOUXE) and the blister beetles, CANTHARID.E, both con- 

 taining a peculiar substance, cantharidin, which renders the 

 'Spanish flies,' an important ingredient of blistering plasters. 



TENEBRIONIDyE. 



Sub _ Order III. TETRAMERA (Cryptopentamera). 

 Tarsi with the penult joint rudimentary, giving the impres- 

 sion of four joints (fig. 472, b). The families numerous in 

 species, are injurious to vegetation. The larvae of CERAM- 

 BYCID.E bore in wood. The CHRYSOMELID^E (Colorado 

 FIG. 473. Ba- potato beetle, Doryphora*} feed on leaves. Sub Order IV. 

 laninus nasicus,* TRIMERA; tarsi with penult and antipenult joints rucli- 

 hazel-nut weevil, mentary, so that they appear three-jointed. COCCINELLID.-E, 

 lady birds, whose larvae, because of feeding on plant lice, 

 etc., are of value to man. Sub Order V. RHYNCHOPHORA, snout beetles; 

 head produced into a long snout with mouth parts at apex. Here belong 

 weevils, which damage grain, nuts, timber, etc. Curculio* Conotrachdus* 

 Calandra,* Balaninus* (fig. 473). 



Order VII. Hymenoptera. 



The Hymenoptera, of which bees, wasps, and ants are well-known 

 representatives, have biting mandibles, while the other mouth parts are 

 elongate and in a minority of the group converted into a sucking organ 

 (p. 406). Since mouth parts vary, the wings and body segmentation 

 have great value in defining the order. The wings are membranous and 

 are supported by few nervures (fig. 474), and in flight they act as one 

 pair, since the two are usually connected by hooked bristles on the hind 

 wing, which engage in a groove on the hinder margin of the front wing. 

 The fore wings are the larger and, correspondingly, the mesothorax 



