56 Memoirs of the Indian Museum. [Voi,. Ill, 



4. Fronto-orhital bristles (or.): a row on each side of the front, variable in 

 number and form. They are divided into superior (i or 2 pairs bent backwards) 

 and inferior or lower (i to 4 pairs bent forwards or outwards). 



5. Genal bristle: on the cheeks, more or less developed. 



6. Occipital row: along the posterior orbits from vertex to chin, rarely 

 wanting. It is formed either by black, thin, pointed bristles, or by whitish, thick, 

 truncated bristles, and has great systematic value. 



Thorax. — Very important is the number and position of the thoracic dorsal and 

 pleural bristles. These are (fig. 2) : — 



Fig. 2. — Side view of the thorax of a Trypaaeid, showing typical chaetotaxy. For explanation of 

 the numbers see text. 



7. Scapular bristles (scp.) : two pairs of small bristles on the fore border of 

 thorax, sometimes less distinct but never wanting; a pair is median or acrostichal, 

 and the other lateral or dorso-central. 



8. Dorso-central bristles (dc): a pair, or very rarely two pairs, in the dorso- 

 central region between the transverse suture and the scutellum, sometimes wanting. 



9. Praescutellar bristles (prsc.) : a pair on the hind border in front of the 

 scutellum, more or less approximate, very rarely wanting. 



10. Humeral bristle (hm.) : on the humeral callus, very rarely wanting. 



11. N otopleural bristles (npl.) or post-humeral of Osten Sacken : two bristles 

 inserted above the dorso-pleural suture in the notopleural depression ; that behind 

 the humeral callus is called anterior and that before the suture ^ is called posterior ; 

 they are always present. 



12. Praesutural bristle (prst.): before the suture and above the praesutural 

 depression, sometimes wanting. 



^ In my paper of 1909 {Boll. d. Lahor, d. Zool. gen. e agaria d. Porlici, III, p. 275, fig. i) I have 

 called this bristle praesutural (calling posthumeral the praesutural) ; but at present I think it better to 

 follow the usual nomenclature. 



