178 W. A. SANDS 



subsidiary marginal tooth of left mandible with proximal end just clear of molar prominence in 

 surface view, complex ratio, La/Li. L m , 8-32-8-45; point of first marginal tooth of right mandible 

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

 length of second, Ra/Ri-Riti, 10-91-11-52. Fore tibia scarcely swollen, Ti/T w , 4-80-5-10, 

 third apical spur vestigial, up to one-quarter length of other two. Mesenteric junction with 

 proctodeum slightly longer than diagonal; enteric valve seating virtually sessile on second 

 pouch of proctodeum, dorsolateral to nearly dorsal in unopened abdomen; enteric valve 

 cushion in position 1 sclerotized throughout its length, half of which protrudes beyond tips of 

 spines of other positions, spines confined to proximal and distal ends, shaft smooth; spines 

 on rim of dilated distal end 14-20 in number, middle part of dilation rounded with scattered 

 fairly long spines, base of shaft fenestrated with a minute spine in each 'hole'; wall of enteric 

 valve seating adjacent to dilated end of position 1, indented and sclerotized in the form of a 

 rounded cup, into which the spines of position 1 fit neatly; this cup sclerotization purplish- 

 brown when fully developed, not yellow-brown as are the cushions of the valve; cushions in 

 other positions with 3-6 elongated curved spines, weakly hooked at tips, and smaller spines on 

 rest of length; membranous wall of valve between and beyond cushions with faint trace of 

 spicules. 



Measurements (two specimens) in millimetres. 



Head width (W) . 



Fore tibia width (T w ) 



Fore tibia length (Ti) 



Postclypeus length (Pel) . 



Left mandible, apical to first marginal 

 (La) 



Left mandible, first to third marginal 

 (L.) 



Left mandible, third marginal to 

 molar (L m ) .... 



Right mandible, apical to first mar- 

 ginal (R A ) 



Right mandible, first to second mar- 

 ginal (R,) 



Right mandible, second marginal to 



molar (Rm) .... 0-05-006 



A. sentosus has already been compared with A. ctenopher, A. muricatus, 

 A. pectinatus, A. rastratus and A. retifaciens, in the descriptions to those species. 

 A . tranquillus differs from A . sentosus in the imago in having a vestigial third apical 

 spur of the fore tibia, a more inflated postclypeus, and proportionately smaller eyes 

 and ocelli, separated by more than the least diameter of the latter. The worker 

 castes are easily recognized by their very distinctive enteric valve armature. 

 A . spinulatus has, again, a distinctive worker caste, with the additional character of 

 longer apical mandibular teeth in both worker and imago, the latter caste also 

 having a proportionately shorter right second marginal tooth. 



It should be noted here that the workers and imago of A. sentosus are associated 

 on a basis of probability rather than certainty, since they were not found together. 

 To do this is always risky, but since the workers have been found both in nearby 

 and in more distant rain forest localities, and no other species is known from the 

 vicinity, the probability that they are correctly associated is high. 







■84-0 



85 





O] 



12 









•59- 



-O 



61 







■19- 



-O 



20 





Ol 



36 







o- 



'3 









•05 



-0 



06 







■ofr 



-007 







•10 



-0 



11 



