44 HYMENOPTERA. 



thorax and head of equal length, the former rounded in front and 

 much compressed behind ; the legs ferruginous, the tips of the 

 joints and the three basal joints of the tarsi dusky; the scale 

 of the peduncle ovate ; the abdomen ovate, with the margins of 

 the segments rufo-testaceous. 



Worker minor. Length 3 lines. Resembles the larger worker in 

 colour, but has the head proportionately more elongate and 

 narrow; the scale is narrower ; the colour of the flagellum differs 

 in being more or less ferruginous, sometimes entirely dusky. 



The female is of the same colour as the workers ; the head is 

 very little wider than the thorax, the latter being elongate-ovate ; 

 the scale is emarginate above ; the legs are shorter and rather 

 stouter. 



147. FORMICA ATRICEPS. B.M. 



Worker major. Length 5 lines. Ochraceous, with the head 

 black : in some examples the head and disk of the thorax are 

 more or less fusco-ferruginous. Head very large, much wider 

 than the thorax and deeply emarginate behind ; the clypeus with 

 a central longitudinal carina, its anterior margin broadly and 

 deeply notched ; the mandibles armed with five blunt teeth ; the 

 flagellum ferruginous. Thorax rounded in front, compressed 

 and much narrowed behind. Abdomen ovate, narrower than 

 the head; the scale ovate, rounded and somewhat narrowed 

 above ; the insect is sprinkled thinly with long erect ferruginous 

 hairs. 



Worker minor. Length 4 lines. Of the same colour as the 

 large worker, but with the head narrower and more elongate ; 

 the clypeus, mandibles and flagellum ferruginous ; otherwise re- 

 sembling the large worker. 



Hab. Brazil (Para; Santarem ; Rio). 



A specimen from the collection of Mr. Swainson, probably 

 the female of this species, is of the same colour as the worker : 

 the thorax ovate, with a dark stain on the mesothorax in front 

 and an elongate dark stripe on each side ; the wings hyaline, 

 the nervures yellow; the scale of the peduncle ovate, with a 

 slight notch above ; the knees, tarsi and apical segments of the 

 abdomen fuscous. 



148. FORMICA ARBOREA. B.M. 



Worker. Length 3^ lines. Opake-black : head large, wider 

 than the thorax, slightly emarginate behind; the scape ferru- 

 ginous at the base ; the clypeus subcarinate, its anterior margin 

 rounded; the mandibles armed with five acute teeth. Thorax 



