i 9 6 W. A. SANDS 



Left mandible, apical to first mar- 

 ginal (L A ) • • • . 007 



Left mandible, first to third mar- 

 ginal (Li) .... 013 



Left mandible, third marginal to 



molar (L m ) .... 005 



Right mandible, apical to first 



marginal (Ra) .... 008 



Right mandible, first to second 



marginal (Ri) .... 0-09 



Right mandible, second marginal 



to molar (R m ) . . . 0-05 



Mesonotum width (M) . . . 0-20 



Metanotum width (N) . . . 0-20 



Worker. Head capsule and pilosity yellow, setae sparse. Postclypeus moderately inflated, 

 Pcl/W, 0-29, Pcl/Ri, 2-26. Apical teeth of mandibles fairly short, L A /Li, 070, R A /Ri, 084; 

 subsidiary marginal tooth of left mandible separated from molar prominence by distinct notch 

 in surface view, complex ratio, La/Li. L m , 1810; point of first marginal tooth of right mandible 

 distinctly behind line of apical to second marginal, anterior edge of first marginal shorter 

 than that of second. Ra/Ri-Riii, 21-60. Fore tibia scarcely swollen, Ti/T w , 5-00, third apical 

 spur vestigial, less than one-fifth length of other two. Mesenteric overlap with proctodeum 

 about three times as long as width of mesenteron at insertion of malpighian tubules; enteric 

 valve seating with two weakly developed opposed lobes and a smaller third inner lobe, connected 

 to second pouch of proctodeum by a distinct neck, dorsolateral in unopened abdomen ; internal 

 cushions of enteric valve all retracted, about equally developed, with scaly surface, posterior 

 margin of each scale with one or more minute points; membranous wall of valve between and 

 beyond cushions with rather numerous minute spicules arranged in curved rows. 



Measurements (one specimen) in millimetres. 



Head width (W) 061 



Fore tibia width (T w ) . . . 0-09 



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



Postclypeus length (Pel) . . 018 



Left mandible, apical to first marginal (La) 0-07 



Left mandible, first to third marginal (Li) . 010 

 Left mandible, third marginal to molar 



(L m ) ...... 0-04 



Right mandible, apical to first marginal 



(Ra) 007 



Right mandible, first to second marginal 



(Ri) 008 



Right mandible, second marginal to molar 



(Rm) 0-04 



In the imago caste, A. amachetus is one of three species in which the back of the 

 head behind the eyes is not evenly rounded. Of the other two species, A . cicur has 

 shorter mandibular apical teeth, a less inflated postclypeus with very indistinct 

 median suture and posterior margin, and a distinctly raised medial spot ; A . improe- 

 latans has wider meso- and metanotal constrictions. In the worker caste, the 

 vestigial third apical spur on the scarcely swollen fore tibia of A. amachetus is 

 diagnostic. The spines of the enteric valve armature further distinguish 



