544 Scientific Proceedings, Royal Dublin Society. 



This species is closely related to the European — indeed cosmopolitan — 

 A. viaticus (Linn.), wherewith it agrees in the straight, stiff bristles of the 

 trunk-segments, in the small anal spines, in the general build of the feet 

 and spring, the nrucro in particular resembling that of A. viaticus almost 

 exactly. The foot, however, of A. caduceator has two (not three) tenent 

 hairs, and an empodial lamella more sinuate than that of A. viaticus. The 

 most definite structural character appears to be found in the acute post- 

 antennal prominences, which are borne on a cylindrical axis (fig. 4). There 

 is a typical retractile vesicle surrounded by four or five sensory hairs at the 

 tip of the fourth antennal segment, and three short sensory spines on the 

 distal edge of the third antennal segment (fig. 5). 



ENTOMOBRYLDAE. 



Genus Isotomina Borner. 



Isotomina xii.-oculata, sp. nov. (PL LI, figs. 11-16). 



Length, l - 25 mm. Six ocelli on each side of head. Post-antennal organ 

 narrowly ovate, as long as diameter of inner anterior ocellus (fig. 12). Feeler 

 as long as head, second and third segments sub-equal, the fourth longer 

 (fig. 11). Eoot-claw, and empodial lamella with distinct internal teeth; 

 forefoot with one tenent hair (fig. 13) ; middle and hind foot with two 

 (fig. 14). Fourth abdominal segment as long as third. Dentes as long as 

 manubrium (fig. 15) ; mucro with three upturned acute teeth (figs. 15, 16). 



Colour of head, feelers, and body deep violet-blue; only the prothorax, 

 legs, and spring pale. 



Locality : Port Herald, Nyassaland. 



^Types in British Museum. 



This species is distinguished from other members of the genus (or sub- 

 genus) Isotomina by the reduction in the number of ocelli to six (instead of 

 the usual eight) on each side, the third ocellus of both inner and outer series 

 being absent. It is not distantly related to /. fasciata Carpenter, 1 from 

 Benin, Southern Nigeria, but the latter has sixteen ocelli, its foot-claws and 

 empodial lamella are without teeth, and its post-antennal organ is shorter 

 and relatively broader than that of the species from Nyassaland now 

 described. The number of specimens collected by Dr. Old is enormous ; all 

 students of springtails know that \xnder favourable conditions these tiny 

 insects present vast assemblages of individuals of the same kind. 



1 Bull. Entom. Research, vol. iii, 1912, pp. 79-80. 



