204 Annals of the South African Museum. 



Most of our South African species nest in the ground, sometimes 

 forming very populous nests containing many hundreds of the 5 

 caste. The ^ ^ of at least all the South African species which I have 

 seen have a very distinctive, although minute character by which they 

 may be recognised. The base of the ventral plate of the 1st abdominal 

 segment forms a pronounced angle with the sides, so that the base of 

 the abdomen has a distinctly truncated appearance. Moreover, in 

 many species the abdomen has a more or less glaucous sheen, giving a 

 steely reflection. These characters can be best observed under a lens. 

 The truncate appearance of the base of the abdomen is certainly 

 noticeable in some other genera, but rarely to such a marked extent 

 as in Monomorium. The specific characters, which when taken 

 together separate our numerous species from, one another, are fairly 

 distinctive, but are often not sufficiently palpable when considered 

 singly, so that it is no easy task to frame analytical keys for all the 

 species. I have endeavoured to draw up a key to include all those 

 species which I have seen, and also a few others which are known to 

 me only from descriptions, but which yet appear to possess characters 

 sufficiently distinctive to be utilised in a table. 



In many species of the genus, e. g., alboj)ilosum, bicolor, etc., the 

 sculpture consists in part of a very fine and even raised reticulation, 

 but under a low magnification only, this has a granulate appearance, 

 owing to the manner in which the light is reflected from the smooth 

 areas enclosed within the reticulations. Such a form of sculpture is 

 described in the following pages as granulate, since its real character 

 is appreciable only with rather high magnification. 



K 



„ ff Key to the $ $ of Monomorium. 



c>(-^trc^a/^ y. Antennae^-jointed (sub-genus Mitara, Forel). 



(3). 2. Yellowish species ; sides of head distinctly, and of 2nd node of petiole, 

 slightly convex . (mictilis, Forel) race atomus, Forel. 



(2). 8. Brownish species ; sides of head and of 2nd node of petiole straight. 



(exiguum, Forel), var. bulatvayensis, Forel. 

 (1). 4. Antennae 12-jointed. 

 (28). 5. Head and thorax dull, or only very slightly shining. 

 (7). 6. Head strongly striate and quadrate . . Emeryi, Mayr. 



(6). 7. Head not strongly striated. 

 (17). 8. Head closely and fairly strongly granulate (see remark in introductory 



paragraph above). 

 (12). 9. Dorsum of epinotum distinctly excavated. 



(11). 10. Dorsum of epinotum deeply excavated. Entirely black, 4 - 2 mm. long; 

 posterior angles of the head prominent, feebly rounded. 



a/rum, Andre. 



