416 Annals of the South African Museum. 



and projects further forwards in front. Dorsum of epinotum generally 

 very short, the teeth obsolete and indicated only by obtuse tubercles. 

 First joint of petiole barely or not at all pedunculate, the node 

 flattened, the posterior face usually dorsal in position. Second 

 node more or less hemispherical, sometimes laterally dentate as in 

 the ^ . Wings as in the ? . 



This genus occurs in both hemispheres and includes a very large 

 number of species, many of which break up into numerous varieties 

 and races. All the South African species with which I am acquainted 

 are omnivorous, Avith a marked fondness for sugary substances, 

 but some species, e. g. excellens, crassinoda and Arnoldi, are mainly 

 graminivorous, harvesting the seeds of grass in the same way as the 

 species of Messor. They do not appear, however, to limit themselves 

 so exclusively to the seeds of one particular kind of grass as in that 

 genus, nor are their stores of seeds so large. Nearly all the species 

 which I have seen usually nest in the ground, and the nest entrances 

 are generally clearly indicated by irregular craters of earth around 

 them. A few species may sometimes be found nesting in hollow 

 trunks of trees, but such a situation is uncommon. The duties of 

 the large-headed soldiers appear to be mainly to remove to and from 

 the nest any matter which is too bulky to be handled by the $ $ , 

 and with their powerful mandibles to dismember the bodies of their 

 insect prey. For purposes of defence they appear to be of very little 

 use, being far less courageous than the small worker. This is easily 

 seen on digging up a nest, when it will be found that the workers 

 attack the intruder, stinging and biting to the best of their ability, 

 while the soldiers immediately seek shelter among the debris, or in 

 the deeper parts of the nest. Nevertheless, if they are sufficiently 

 irritated, they will also attack, and bite so firmly to the skin of the 

 hand that they will allow themselves to be torn in half rather than 

 loosen their hold. 



The species of this genus are pre-eminent in their readiness to 

 harbour other insects in their nests. In Rhodesia it is in the 

 nests of P. punctiUata that one may most frequently find such 

 myrmecophiles, especially Paussidae, Clavigeridae and Pselaphidae. 

 Amongst the $ £ au< ^ 2 9 °£ the genus, there is a general uniformity 

 of structure which renders the determination of the different species 

 a difficult matter, so that it is essential that examples of the "2/ 

 caste should be obtained, in which a greater specific diversity is 

 apparent. 



In the treatment of this genus I have endeavoured to arrange 

 the species into groups, such grouping being based chiefly on the 



