FORMICIDAE — ANTS 



133 



(notal) pieces are frequently obliterated in the workers, while 

 they are distinct in the males and females, and the pieces them- 

 selves are also much larger in size in these sexed individuals. 

 The pro-mesothoracic stigma is 

 apparently always distinct ; the 

 meso-metathoracic one is distinct 

 in the male Dorylus, but can scarcely 

 be detected in the winged forms of 

 other ants, owing to its being en- 

 closed within, and covered by, the 

 suture between the two segments : 

 in the workers, however, it is usually 

 quite conspicuous. The posterior 

 part of the thoracic mass, the pro- 

 podeum or median segment, is of 

 considerable size ; no transverse 

 suture between the component pieces 

 of this part can be seen, but its 

 stigma is always very distinct. The ^,^, zi.-Oecodoma cephaMes. South 



peduncle, or pedicel, formed by the America. A, Worker major ; B, 



1 1 1-1 , female after castiiiEr the wings. 



extremely mobile segment or seg- ^ ^ 



ments at the base of the abdomen (already noticed as form- 

 ing the most conspicuous character of the family), exhibits much 



Fig. 56. — Stridnlating organ of an ant, Myrmica rubra, var. laemnodis. Sagittal section 

 of part of the 6th and 7th post-cephalic segments. (After Janet.) a, a}, muscles ; 

 &, connecting membrane (corrugated) betAveen 6th and 7th segments : c, 6th seg- 

 ment ; d, its edge or scraper ; e, striate area, or file on 7th segment ; /, posterior 

 part of 7th segment ; g, cells, inside body ; A, trachea. 



variety. Sometimes the first segment bears a plate or shield 

 called a scale (Fig. 53, A, &); at other times there are two 



