85 



ON THE ETHIOPIAN FRUIT-FLIES OF THE GENUS DACUS. 



By Prof. M. Bezzi, 

 Turin, Italy. 



The rather numerous Ethiopian species of Dacus (s.l.) are very homogeneous 

 owing to their reduced chaetotaxy and the very simple pattern of the wings ; they 

 have no praescutellar bristles, only a scutellar pair, and very often only two 

 supra-alar bristles, the anterior one being wanting. There are no species with a 

 stalked abdomen, or with spinose femora, or with elongated antennae, or with, 

 banded wings. 



In the more numerous and differentiated Oriental species the praescutellar bristles 

 are, on the other hand, usually present, and very often there are two pairs of 

 scutellar bristles ; the anterior supra-alar bristle is almost always present. I have 

 therefore separated the Oriental (and Australian) species into the two genera 

 Bactrocera (with banded wings) and Chaetodacus (with the wings not banded) ; and 

 recently I have added the new genus Monacrostichus for the species with elongate 

 antennae, spinose femora and stalked abdomen, and which also lack the praescutellar 

 bristles. 



Fig. 1. Side view of the thorax of a Dacus, to 

 show the chaetotaxy : — scp, scapular bristles ; 

 n'pl, notopleural bristles ; mpl, mesopleural ; 'pt, 

 pteropleural ; asa, anterior supra-alar ; p.sa, 

 posterior supra-alar ; a, apical bristles. 



It is interesting to note that there is also a small but remarkable difference in 

 the sexual wing-dimorphism. In the males of the Oriental species the wing shows 

 on the hind border at the end of the anal vein a deep sinuosity, the third posterior 

 cell being therefore produced like a second axillary lobe ;* the males of the Ethiopian 



* This sexual dimorphism was first described by Prof, de Meijere (Tijdschr. Entom., 

 xli, 1908, p. 127) and subsequently by Hendel {Supplem. entom., i, 1912, p. 13), both 

 working on Oriental species. But there are some true Chaetodacus without this lobe, 

 such as C. garciniae, Bezzi, and G. bipustulatus, Bezzi ; C. cucumis, French, has no 

 lobe, but also no praescutellar or anterior supra-alar bristles, and is therefore a true 

 Dacus {s. str.), 



(C177) Wt.P8/91. 1000. 9.15. B.& F.Ltd. Gp.11/1. a 



