THE SOLDIERLESS TERMITES OF AFRICA 



93 



Worker. Head capsule yellow-white, pilosity pale yellow, sparse, inconspicuous. Post- 

 clypeus weakly to strongly inflated, Pcl/W, 0-24-0-35, Pcl/Ri, 1-89-2-97; apical teeth of mandibles 

 short, L A /Li, 0-43-0-54, Ra/Ri, 0-57-0-76; subsidiary marginal tooth of left mandible just clear 

 of molar prominence in surface view, complex ratio, La/Li. L m , 7*25— 11-41; first marginal of 

 right mandible distinctly behind line of apical to second, its anterior margin half length of second 

 or less, Ra/Ri Rm. 994-1308. Fore tibia scarcely inflated, Tj/T w , 4-21-5-52, third apical 

 spur distinct, about one-third length of other two. Mesenteric junction with proctodeum 

 diagonal, to right of malpighian knot; enteric valve seating dorso-lateral in unopened abdomen, 

 weakly two-lobed, sessile or second pouch of proctodeum or with very short neck ; membranous 

 wall of valve beyond cushions with sparse minute spicules. 



Measurements (20 specimens from 20 localities) in millimetres. 



Head width across eyes (W) . 



Fore tibia width (T w ) . 



Fore tibia length (Ti) .... 



Postclypeus length (Pel) 



Left mandible, apical to first marginal (L A ) 



Left mandible, first to third marginal (Li) 



Left mandible, third marginal to molar (L m ) 



Right mandible, apical to first marginal (Ra) 



Right mandible, first to second marginal (Ri) 



Right mandible, second marginal to molar (R, n 



Range 

 0-71-0-90 

 010-014 

 0-50-0-66 

 0-18-0-29 

 005-008 

 0-11-0-15 

 004-006 

 005-008 

 0-09-0- 1 1 

 004-006 



Mean ± S.D. 

 0791 ± 0055 



0-122 4_; OOO9 



0-583 ± 0-048 

 0-229 ± 0029 

 0064 i 0007 

 0-129 ± 0008 

 0052 ;£ 0-006 

 0-064 i 0007 

 0099 ± 0008 

 0056 ±: 0006 



A. quietus is another variable species, which closely resembles A. brevior in some 

 of its forms. The differences have already been discussed under that species. The 

 variation in the degree of development of the postclypeus and its median suture is 

 of particular interest. This is most marked in the worker but is reflected in the 

 corresponding imagos. The species has been found in a range of habitats from deep 

 rain forest to small thicket clumps in the savanna zones or even in mounds of other 

 species in open savanna. In the forest specimens the postclypeus tends to be 

 least developed, often lacking a median suture in the imago. The savanna forms 

 have a well developed postclypeus and median suture. The postclypeus is the point 

 at which the cibarial dilator muscles which lift the roof of the buccal cavity are 

 attached. It is therefore probable that the increasing size of the postclypeus in 

 drier conditions accommodates larger muscles better adapted to work the drier 

 soil on which the termites feed. This admittedly speculative interpretation of 

 directional variation appears reasonable in view of the poor flying and hence dis- 

 persive powers of these small termites which would tend to perpetuate locally 

 adaptive variants. The same characters of A. obstructus that separated it from 

 A. brevior also serve to distinguish it from A. quietus. Of the other species of 

 Astalotermes, A. benignus and A. concilians are sympatric with A. quietus. The 

 small size of A. benignus and the vestigial third apical spur of the fore tibia are 

 distinctive; in A. concilians the postclypeus is usually more inflated, the meso- 

 and metanota narrower in the imago, and the first marginal tooth of the right man- 

 dible is larger. The phenomenon of worker abdominal dehiscence apparently 

 reaches its peak with A . quietus in which it is difficult to find an unburst specimen 

 for dissection in most nest -series. 



A lectotype has been designated below from the syntype-series of A. quietus. 



