144 Annals of the South African Museum. 



Characters. 



$ . Monomorphic. Frontal area more or less distinct. Antennae 

 12-jointed, 11-jointed in Semonius. Sting rudimentary, except in 

 the Ceylonese genus Aneuretus. Middle and hind tibiae with one 

 pectinate calcar, occasionally there is a small outer calcar. 



5 . Always winged ; like the worker except for the usual sexual 

 differences. 



S . Clypeus prolonged backwards between the frontal carinae. 

 Mandibles as in the £ , or short and narrow. Antennae 13-jointed, 

 the scape is not longer than the second joint of the flagellum except 

 in Tapinoma and Semonius. 



Nymphs never enclosed in cocoons. 



The classification of this sub-family, especially in the definition of 

 the genera, is based largely on internal anatomical characters, such 

 as the structure of the gizzard. As we have only three indigenous 

 genera, including very few species, it has fortunately not been found 

 necessary to burden the description of the genera with these difficult 

 details, which can only be observed with the aid of fine dissections. 



All the workers of the Dolichoderinae possess anal glands which 

 produce a secretion hardening on exposure to the air, and usually of 

 an unpleasant odour. This secretion is used as a means of pro- 

 tection, since its stickiness serves to clog the limbs of other insects 

 which may attack these ants. 



All our species, with the exception of the introduced Iridomyrmex 

 humilis, the "Argentine ant," are shy inconspicuous insects, 

 forming only moderate-sized colonies. Iridomyrmex humilis, whose 

 original home was probably in Brazil, is an ant which has recently 

 spread through a large part of the globe. Its appearance in 

 South Africa would appear to date from the time of the last Boer 

 War, when it was probably introduced with forage. It is very 

 common all over the Cape Peninsula, and in the neighbourhood 

 of Gape Town it is not only a great pest in houses, but is also the- 

 dominant species. Thus on the slopes of Table Mountain very few 

 ants of other species are to be found below the 800-1,000 ft. level, in 

 which area humilis is exceedingly plentiful ; above that level it is 

 very rare, if not altogether absent, whereas other genera, e.g. 

 Plagiolepis, Ocymyrmex, Tetramorium, are more commonly repre- 

 sented. The astonishing paucity of species and genera at the lower 

 levels of the mountain, and the absence of I. humilis in the higher 

 is probably due to two causes, namely, the non-dolichoderine species 

 cannot survive in competition with the Argentine ant, and the latter 

 is unfavourably affected by the climatic conditions of the higher 



