OBSERVATIONS ON SOME SOUTH AFRICAN TERMJTKS. 387 



wall in a nearly regular manner all round. The building- 

 insects move up the walls of the air-pit in great numbers, 

 like so many bricklayers, eacli adding its quota of material 

 to the structure. Whilst this work is proceeding, the 

 thickening of the rim is done by insects working within the 

 chimney wall, and although the edge of the ring is quite 

 thin whilst the work is in ])rogress, yet, when the required 

 height is reached, the wall of the chimney is thick through- 

 out. Chimney building is not conducted all the year round, 

 but is frequently to be seen in progress during spring and 

 summei". 



In most cases the chimney is seldom more than 6 to 8 in. 

 high. The highest observed in Natal was 20 in., but in the 

 Transvaal and Orange Free State some chimneys are carried 

 up to between 2 and 3 ft. (PL XXXI, fig. 6). 



It has yet to be shown by exact experiment that currents 

 of air pass up the taller of these structures ; but that the pits 

 of which they are the chimneys are for the aeration of the 

 nest there can be no doubt. Nor is there any doubt that the 

 chimneys, or rims as the case may be, are for the purpose of 

 preventing any inrush of water. It is seldom that the air- 

 chambers are filled with soil by weather effects ; but instances 

 have been noted — the nests so affected being on footpaths 

 worn in the veld by the natives — where tori-ents of water 

 during rain storms have poured into them. 



The air-chambers may be of great size and flask-shaped, or 

 they may be but deep vertical shafts, in which case they have 

 equally large branches (PI. XXIX, fig. l,a). They are 

 associated with the large main hives made by this species and 

 connect with them by only a very few small galleries, just 

 sufficiently large for two insects to pass one another. It is a 

 feature of the mound and super-mound of latericius that 

 no galleries are driven through them, and this fact strongly 

 suggests that the great shafts in the mounds of the 

 bellicosus group act largely in aerating the hives, althouo-h 

 they have no actual apertures. The main hives contain a 

 vast extent of fungus-bed; but, as they are more than half 



