65 



ON THE RUBBER THRIPS (PHYSOTHRIPS FUNTUMIAE, BAGN.) 



AND ITS ALLIES. 



By Richard S. Bagnall, F.L.S. 



The rubber thrips deserves to be more widely known, not only on account of its 

 economic importance, but because it forms the type of a small group of the genus 

 Physoihrips, separated at once by the structure of the sternites 3 to 7 in the (J. 

 In some species the sternites are simple, but in most they are characterised by one 

 well-formed and defined thinly chitinised area in the centre of each, either round, 

 transverse or oviform, generally largish but sometimes reduced to a small puncture- 

 like depression. These male features are found also in other genera. In P. fun- 

 tumiae and its allies however the sternites 3 to 7 have numerous, usually irregular, 

 depressions, smaller or greater, arranged in 2 to 4 more or less regular or denned 

 transverse rows. In one species (P. funtumiae) the anterior row of areas is charac- 

 terised by the possession of a long, transverse, median area ; but this is occasionally 

 broken up to a greater or less degree. 



I now give tables and figures of the three species falling into this group, from which 

 it will be seen that other features of more than usual interest exist. I would refer 

 chiefly to the antennal antigeny in two species. 



Stated briefly we find that the antennae — ■ 



(a) are the same in both sexes, both as regards colour and structure, in P. mar- 



shalli ; 



(b) agree in structure, but differ in colour, in the sexes of P. funtumiae ; 



(c) agree in colour, but differ in structure, in the sexes of P. Icellyanus. 



Sexual dimorphism in the direction of (6) is quite usual in the Terebrantian 

 Thysanoptera, but in the direction of (c) it is of much rarer occurrence. 



In 1915, however, Hood (Proc. Ent. Soc. Washington, xvii, pp. 128-132) charac- 

 terised the new genus Plesiothrips for Thrips perplexus, Beach, the discovery of 

 the $ illustrating a more extreme case of antennal antigeny than in P. marshalli. 



I have pleasure in naming the new species in honour of my good friend, Dr. Guy 

 A. K. Marshall, Director of the Imperial Bureau of Entomology. 



Table of Females. 



1. Fore- wings uniform brown. Fringe of posterior margin of tergite 8 distinct, 

 longish. Chaetotaxy less strong ; bristles of pronotum normal. Antennae 

 either similar in the sexes or exhibiting dimorphism in colour. Size smaller. 



Hab. Africa . . . . . . . . . . . . 2 



Fore- wings with basal fourth or thereabouts white. Fringe of tergite 8 vestigial, 

 medianly lost. Chaetotaxy stronger ; pronotum with a pair of minor setae 

 within the postero-marginal pair. Antennae exhibiting sexual dimorphism in 

 structure. Size larger. Hab. Australia . . . . ..P. kellyanus. 



(C455) e 



