INTKODUCTJON. VU 



iu the d from what they are in the ? or $ ; h, scape, j, 

 flagelluni, the two united forming the antenna: the scape or 

 basal joint, except in the rf of certain species, is always longer 

 than any of the other joints, these latter are often greatly 

 modified in relative size and thickness, but in the great majority 

 the apical joint of the flagellum is the longest and broadest; 

 k, k, compound eyes, which may be present or absent, and com- 

 posed of few (one to five) or many facets. The softer mouth- 

 parts of ants are similar to those of typical Hymenopterous insects 

 fully described at p. iv of the Introduction to Vol. I. of the 

 Hymenoptera in this series. Owing probably to the small, often 

 minute size of the vast majority of ants, the mouth-parts have not 

 been much used in determining the classification. Fig. iii repre- 



Moutb-parts of Camponotus $ . 



sents the maxilla (A) and labium (B) of one of the Camponotince. 

 In A : , stipes ; 6, galea ; c, palpus. In B : a, ligula ; b, b, palpi. 

 The thorax in ants varies enormously in shape and development 

 of the component parts. The thorax of a $ , as already stated, 

 differs markedly from the thorax of the $ or rf of the same 

 species, except in the case of ergatoid males and females. 

 I igs. iv-viii illustrate partially the forms of the thorax in the five 

 subfamilies ; but as the genera vary greatly among themselves, no 

 form can be selected as in any way typical, and reference should be 

 made to the illustrations in the body of the text for the peculiar 

 form of thorax assumed by any genus. Taking the Poncrince for 

 example, fig. iv and fig. v (B & C) represent the thoraces of 

 one of the species in the $ , rf and . The parts are : a, the 

 pro thorax, generally forming a portion of the dorsum in the $ as 

 in fig. iv, but often .suppressed beneath the mesonotum in the 3 , 

 fig. v, B, and also in the $ , fig. vi ; in the , fig. v, C, and 

 figs, vii & viii, it is level with the mesonotum ; 6, the mesothorax 

 with its scutellum c, the latter often nearly or quite suppressed 

 and rudimentary ; o, the postscutellum or upper portion of the 

 metathorax is often (nearly always in the $ ) completely obsolete, 

 but d, properly the median segment, has, according to usual 



62 



