CLASSIFICATION 



321 



is distinguished by a combination of characters which all 

 its members have in common. It is necessary, however, to 

 realise that classifiers of insects often differ among them- 

 selves as to what they mean by a family. Several of the 

 groups just mentioned as families are regarded by many 

 writers as " superfamilies " ; J. H. Comstock, for example, 

 in his recent handbook (1924) reckons eight families of 

 Symphyta and forty of Apocrita in a systematic treatment 

 of the Hymenoptera. 



Fig. 77. — a, Dorsal aspect of front half of Wasp (Vespa), showing 

 prothorax (black area) reaching back to tegulae at wing-bases ; b, corre- 

 sponding region of a Chaicid, in which the prothorax (black area) does 

 not extend backwards ; c, part of leg of Vespa with undivided tro- 

 chanter (tr) ; d, the same of a Chaicid with divided trochanter ; 5^, " short " 

 face of a ground-wasp {Vespa germanica) ; n, " long " face of a tree-wasp 

 {V. norvegica). Magnified. 



Every family of insects comprises a number of genera ; 

 rarely do we find a monotypic family with only one genus. 

 It may be noted that a family name in systematic zoology 

 is formed from the root of the generic name with the termina- 

 tion 'idae. Thus the family name for the true Wasps — 

 Vespidae — is formed from Vespa, the name of the typical 

 genus. 



In these countries there are two genera of Vespidae, 

 each with several species and each representative of a distinct 



Y 



