518 Transactions South African Philosophical Society, [vol. xiii. 



Gen. PLAGIOCHILUS, Wasm., 

 Illustr. Zeitsch. f. Entom., v., 1900, p. 5, p. 82. 



The characters differentiating this genus from Cosnochilus are 

 the shape of the prothorax, which is ampliate rounded at about the 

 median part and straight or only slightly sinuate thence to the 

 outer angles which are acute, and of the spiracle of the last abdominal 

 segment which is spiniform. The elytra have two geminate striae on 

 each side of the suture, and the pygidium is strongly swollen in the 

 centre. Wasman, who founded the genus on P. intrusus, ascribes to 

 it " small eyes nearly obsolete and not visible from above or in 

 front"; this is not the case, however. Wasman included also in 

 the genus P. setosus (Burm.), which he took to be a new species and 

 named P. argenteus, and in which the eyes are very large, and the 

 shape of the clypeus, as well as that of the mentum, is very different 

 from that of P. intrusus. 



This genus is thus not very homogeneous, unless it be divided into 

 two sections : — 



I. C 2 . Clypeus very convex in the centre, emarginate in front. 

 II. Clypeus not convex, marginate in front. 



The species seem to be all myrmecobious. C. angustatus, 

 Westw., from Guinea, will also have to be included in the genus. 



Key to the Species. 



A 2 . Ligular part plane on the outer part, incised or emarginate in 

 front. 



B 2 . Clypeus very convex. 



Ligula incised ; prothorax with round punctures ; elytra 

 quadri-striate and quadri-costulate on each side intrusus. 



B 1 . Clypeus plane, marginate and reflexed in front. 



Ligula sinuate in front ; prothorax transversely plicate with 

 a white lateral margin ; elytra not distinctly costulate, 

 cicatricose punctate and each with six rows of minute 

 squamose hairs diversus. 



Ligula slightly sinuate in front, body very hairy ; prothorax 



reticulate punctate ; elytra non-costulate, scabrose punctate tomicoides. 



A 1 . Ligula bulging strongly on the outer face. 



Body briefly pubescent ; head with a median tubercle ; pro- 

 thorax with a broadly oval impression on the disk corniger. 



Body pubescent, head simple, prothorax not impressed, strongly 

 reticulate; elytra roughly reticulate punctate and with one 

 dorsal costa. suture raised .. . . setosas. 



