62 \V. A. SANDS 



Right mandible, apical to first 







marginal (Ra) 



006 



— 



Right mandible, first to second 







marginal (Rj) 



008 



— 



Right mandible, second mar- 







ginal to molar (R m ) 



0-05 



— 



Mesonotum width (M) . 



0-15-018 



0165 



Metanotum width (N) . 



014-0-19 



0166 



Worker. Head capsule yellow, pilosity orange-yellow, numerous and rather coarse, short. 

 Postclypeus rather strongly inflated, Pcl/W, 0-29-0-30, Pcl/Ri, 2-35-2-55. Apical teeth of 

 mandibles fairly short, La/Li, 0-58-0-61, Ra/Ri, 0-71-0-80; subsidiary marginal tooth of left 

 mandible just clear of molar prominence in surface view, La/Li. L m , 15-19-16-50; apical and 

 marginal teeth of right mandible approximately in line, anterior edges of marginal teeth equal, 

 Ra/Ri-Riti, 19-00-19-39. Fore tibia weakly inflated, Ti/T w , 4-22-4-34, third apical spur vestigial. 

 Mesenteric junction with proctodeum slightly longer than diagonal, to right of malpighian 

 knot; enteric valve seating dorsolateral in unopened abdomen, weakly two-lobed, connected 

 to second pouch of proctodeum by short neck, membranous wall of valve beyond cushions 

 with sparse minute spicules. 



Measurements (two specimens from two localities) in millimetres. 



Head width (W) ... 0-65-0-66 



Fore tibia width (T w ) . . . o-io 



Fore tibia length (Ti) . . . 0-43-0-44 



Postclypeus length (Pel) . . 0-19 



Left mandible, apical to first marginal 



(L A ) 0-06 



Left mandible, first to third marginal 



(Li) ...... o-io 



Left mandible, third marginal to 



molar (L m ) .... 004 



Right mandible, apical to first mar- 

 ginal (Ra) ..... 0-06 



Right mandible, first to second mar- 

 ginal (Ri) ..... 0-08 



Right mandible, second marginal to 



molar (R m ) .... 004 



The vestigial third apical spur of the fore tibia distinguishes this small species 

 from its closest relatives, A. concilians in particular since it is sympatric. The other 

 species with a vestigial spur are much larger in Group II, and A. benignus is in any 

 case unique in the genus in having the spur reduced to this extent in both castes. 

 It also differs from A. amicus and A. eumenus, and A. comis in the proportions of 

 the mandibular teeth. The abdomen of the worker is definitely dehiscent in 

 A. benignus. 



Holotype $ imago, paratype $ and $ imagos, and workers from type-colony, 

 Guinea: Mt. Nimba, Pierre Richaud, 10.viii.1951 (M. Lamotte coll. No. 18 Pa. 392), 

 in American Museum of Natural History (paratype $ and worker from type-colony 

 alsoinBMNH). 



Other paratype material. Guinea: Mamou, io°2o'N., i2°i5'W., 25.viii.1912 



