&! MEDICAL ENTOMOLOGY 



terms, on the episternum of the mesothorax, near its upper and posterior 

 angle) ; the sternopleural, on the mesosternum, below the suture between 

 it and the episternum (mesopleura) ; pteropleural, rarely present ; meta- 

 plettral or trichostichal, on the metapleura ; and hypopleural, usually 

 small, on the hypopleura. 



On the abdomen : Marginal bristles, situated on the posterior margins 

 of the tergites ; discal, on the tergites but removed from the margins ; 

 and lateral, near the lateral margins of the segments. 



The following terms are used to denote the inclination of the bristles 

 or groups of bristles : erect, stiberect, proclinate, reclinate, convergent, 

 decussate, or cruriate. The bristles themselves are described as strong, 

 weak, represented by hairs, hair-like, or normal with hairs among the 

 bristles. The arrangement of a group may be in a single row, in more 

 than one row, parallel, convergent, or divergent ; they may be apical, 

 as on the scutellum, or sub-apical ; arranged in pairs or singly. The 

 actual number is always stated unless large. 



The application of the above nomenclature requires a good deal of 

 experience, and it is of great advantage to obtain a few named and de- 

 scribed specimens, and to compare the chaetotaxy with the description 

 of the fly by a recognized authority. 



