16 



CHAETOTAXY. 



frontal group of Hough, lor. cit.) ; orbital bristles absent in 

 both sexes ; vihrissal angle (separated by a well-marked and 

 rather wide interval from the oral margin) without a large and 

 conspicuous vibrissa ; vihrissal ridges ciliated to a point on a level 

 with or rather above the middle of the third joint of the 

 antenna. 



llioracic bristles. — The general arrangement, as can be seen 

 from the accompanying diagrams, is, on each side, as follows : — 



Dorsal aspect (Fig. 9). — Humeral, from 1 to 3 (sometimes 

 apparently 4), the lowest bristle the largest. Post-ltumeral (intra- 

 humeral of Osten Sacken) absent. Notopleural (of Girschner 



Przsutural Bnstle v 



PreBsutural 



dorso -centra I Bristle 



2"''dorso-central 

 Brist/e , 



1 dorso-central 



Bristle 



MerginsI scutellar Bristle ,_ 

 Apical scutellar Bristle --_ 



fW-':~-^-'^~ l-lumeral 8risC/es 



Notop/eural Bristles 



/ (of Girschner snd Haugti 

 post-humerol of Osten 

 Sacken .) 



.^Supra-alar Bristle 



Intra-alar Bristle 



=^i^ Post-alar Bristles 



Inner dorso-central 

 Bristle 



Fig. 9. 

 Diagram of thoracic chaetotaxy of Glossina, dorsal aspect. (X 10.) 



and Hough, post-humeral of Osten Sacken), 2. Praesutural, 1.* 

 Supra-alar, 1. Intra-alar, 1, situated just in front of the post- 

 alar callus, on a level with the second dor so-central. Post-alar, 3, 

 the foremost somewhat smaller than the other two, and placed 

 directly above the alar frenum. Dorso-central, 3, two near 

 together, close to the hind margin of the dorsum, and one 

 immediately in front of the suture ; the latter bristle may be 

 termed the praesutural dorso-central. Inner dorso-central, 1, near 

 the hind margin of the thorax. Scutellar, 2, one marginal (near 

 the basal angle), the other apical ; additional scutellar bristles 

 are occasionally found. 



The relative size of the variovis bristles enumerated above is 



Often small and difficult to distinguish in G. palpalis. 



