136 W. A. SANDS 



of the more northern Cape Province and Transvaal at altitudes from i,6oo to 3,000-4,000 feet. 

 It also occurs in parts of Natal and the Orange Free State. 



In the moist lowlands of Zululand the smallest and palest coloured specimens are found, and 

 these if placed alongside the fuscus form appear completely dissimilar. The gradual change 

 can be followed inland with specimens from increasing altitudes through Natal to the uplands 

 of Transvaal. 



I have considered retaining the specific names of the synonyms to designate 

 subspecies ; in view of the occurrence of every gradation of intermediate between 

 the variants, and of apparent exceptions to the geographical distributions outlined 

 above, I believe it is inadvisable to do so at present. 



The situation in T. trinervoides would seem to be as follows : 



It is the only species of Trinerviternies inhabiting the limits of subtropical and tem- 

 perate South Africa. In so doing it has left behind congeners which might compete 

 with it. South Africa has a very wide range of ecological conditions, which have 

 given rise to correspondingly wide variation in this species. Whether or not the 

 forms recognized constitute true allopatric subspecies, sections of one or more 

 clines, or genetically heterogeneous variants of similar appearance induced by similar 

 ecological conditions in different areas (" polytopic " subspecies, Mayr, 1953) can 

 only be shown by further studies. It may be noted that a "fuscus "-like form of 

 T. dispar has also been found at an altitude of 3,000-5,000 feet in Natal, perhaps lend- 

 ing weight to the latter suggestion. It has also been observed that the nose-length of 

 soldiers of all species and genera tends to be greater in the drier steppe vegetation 

 of the interior. 



The smaller specimens of T. trinervoides resemble T. rapulum in both imago and 

 soldier castes. In addition to the characters given in the keys, the imago has usually 

 a larger and differently shaped fontanelle and the head viewed from above is straight 

 between the ocelli rather than indented in the middle around the fontanelle. The 

 soldier has a much more hairy nose tip, and is distinguished from both T. rapulum 

 and T. rhodesiensis by the rounder plan view of the head capsule. The imago 

 differs from T. rhodesiensis in having the ocelli further from the eye, and the ventral 

 " scent " gland distinctly smaller. 



The larger, more typical specimens of T. trinervoides are unlikely to be confused 

 with either of their partly sympatric congeners. The 9 or 10 ridges on the molar 

 plate of the right imago mandible are a useful additional character, and the $ cerci 

 are usually shorter. 



Type Material. Republic of South Africa : Cape Province, Laingsburg, no 

 date (Brunnthaler) , syntype $ imago and soldiers, type colony, T. trinervoides 

 (Sjostedt), A.M.N.H., (other syntypes in Naturhist. Riksmus., Stockholm) ; Natal, 

 Pinetown, 1905 (/. Trdgdrdh), syntype soldier, type colony, T. trinerviformis 

 Holmgren, A.M.N.H. and B.M.(N.H.), (other syntypes in Naturhist. Riksmus., 

 Stockholm) ; Cape Province, Somerset West, Pearston, xi.1920 (F. Thomsen), 

 syntype $ imago and soldier, type colony, T. gemellus ssp. thomseni Fuller, A.M.N.H. 

 (other syntypes in N.C.I., Pretoria) ; Natal, Haviland Rail, 1894 (G. D. Haviland), 

 syntype soldiers from type colony, T. havilandi Fuller, A.M.N.H. and B.M.(N.H.), 



