FORMICIDAE ANTS 



133 



(iiotal) 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 Doryhis, 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 

 peduncle, or pedicel, formed by the 

 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. 55. — Oecodomu cephalotes. South 

 America. A, Worker major ; B, 

 female after casting the wings. 



Fig. 56. — Stridiilating organ of an ant, Myrmica nihra, var. laevinodis. Sagittal section 

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

 h, connecting membrane (corrugated) between 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 ; /;, trachea. 



variety. Sometimes the first segment bears a plate or shield 

 called a scale (Fig. 53, A, 5) ; at other times there are two 



