24 H. C. EFFLATOUN. 



Pitt. Eritrei., II. 21.75. (1908) et Syrph. aethiop. Mus. Nat. hun- 

 garici, 132. (2).5. {tibialis var.) (1921). 



dimidiatus Lw, Berl. Entom. Zeitschr., VII. 308.68. (1863) ; 

 Willist., Bull. Unit. Stat. Nat. Mus., (31), 20. (1886) et Biolog. 

 Centr. Amer., Dipt., III. 5.1. (1891); Towns., Psyche, VIII, (259), 

 140. 2. et (260)., 147.2, (1897); Aldr., Catal. N.A. Dipt., 351. (1905). 



tacchetii Rond., Atti. Soc. Ital. Sci. Nat. Milano, VIII, 

 140. (1865). 



varipes Big., Anna! Soc. Entom. Fr., (5). X. 150.° (Orthonevra) 



(1880) et (6). V.' 249 (Orthonevra) (1885). 



auricaudatus Big., Annal. Soc. Entom. Fr., (6). III. 1883. 

 540. 2. (1884); Willist., Bull. Unit. Stat. Nat. Mus, (31), 301. 

 (1886). 



DIAGNOSIS: — Fact with a black middle line in both sexes ; 

 scutellum entirely black in both sexes. 



DESCRIPTION : —Male : Face from light to dark shining 

 yellow with a black middle line which extends from between the 

 antennae to the upper mouth-edge; this line is rattier widened about 

 it's lower part and is produced quite one third of the width of the 

 eye. Pubescence delicate white and equal everywhere except on the 

 middle line. Jowls small with white pubescence which is continued 

 on to the occiput. Vertex shining black, elongate and very pointed 

 in front and possesses inconspicuous blackish pubescence. Eyes 

 touching for a short distance and with short inconspicuous 

 whitish pubescence which has no tendency to run into stripes. 

 Antennae with the two basal joints black ; the rather long 

 third joint which is usually about three times as long as broad 

 is generally black above and yellow below ; arista brown, bare and 

 not quite as long as the third antennal joint. 



Thorax aeneous-black, shining, and rather coarsely punctate; 

 it is clothed with fairly abundant and erect whitish pubescence, 

 which is winter and much longer on the pleurae. Scutellum with a 

 similar pubescence as that of the thorax and without any trace of 

 light colour. 



Abdomen shining black, with a punctuation which is coarser 

 on the basal half, but the extreme hind margins of the segments 

 are impunctate and very shining; sometimes it bears orange-red or 

 yellow markings, which colour may extend on to all the segments, 

 except the basal one, such as in the varieties mentioned below. 

 The second segment is longer than the basal, the third longer than 

 the second, the fourth longer than the third, and the fifth is much 

 shorter than any of the four others but is very obvious ; the abdo- 



