Genera ontl Species o/'TabaiikUe. 5 



tlic British Museum (Natural History), — Adersia would 

 appear to be distinguishable inter alia by the eyes being 

 devoid of liair and the body comparatively bai'e, by the 

 second ubdoiuiual segment not being abuormaily large, and 

 by the wings not being of relatively unusual length. The 

 small, almost minute size of the proboscis Avill aloue suffice 

 t) distinguish Adersia from any other genus of African 

 Tabauidte at present known. 



The author has much pleasure in naming this new genus 

 in honour of Dr. W. M. Aders, who, during his sojourn in 

 Zanzibar, has j)aid special attention to its blood-sucking flies, 

 and has materially increased our knowledge of the Dipterous 

 fauna of the island. 



Adersia cestro'ides, Karsch. 



Silvius astro'ides, Karscb, Bed. Eut. Z., Bd. xxxi. p. 371, Taf. iv. fig. 1 

 (1887). 



[Since this species was originally described from an 

 imperfect female, while both original description and figure 

 leave much to be desired, no apology is needed fjr publishing 

 the following redescriptiou, which is based on both sexes, a 

 number of specimens of each of which, in excellent con- 

 dition, were fortunately obtained by Dr. Aders. The present 

 writer desires to express his acknowledgments to Dr. K. 

 Griinberg, of the Konigliches Zoologisches Museum, Berlin, 

 Avhere the type of the species is preserved. With obliging 

 courtesy Dr. Griiubcrg, at the request of the writer, carefully 

 compared one of Di'. Aders's specimens with the type, and 

 as a result formed the opinion that the two specimens are 

 conspecific, — a conclusion with which the writer, after 

 studying tlie notes kindly furnished to him by Dr. Griinberg, 

 entirely concurs. It should be added that the type of the 

 species, which is from the mainland (Usambard, German 

 East Africa), is considerably larger than even the largest af 

 the females obtained by Dr. Aders, which themselves exhibit 

 considerable variations in size. According to Dr. Griinberg, 

 the type measures 15'5 mm. in length, while, as will be seen 

 below, the maximum length of the females from Zanzibar is- 

 13*5 mm.] 



^ ? . — Length, cJ (6 specimens) 9-8 to 10 mm., $ (13 

 specimens) 10 to 13"5 mm.; width of head, ^ 2'7o to S'2 

 mm., ? 2*8 to 3*75 mm. ; width of front of J at vertex 

 0'75 mm., width of front of ^ in centre 0*25 mm.,^ width of 

 front of $ 1*25 to 1*6 mm. at vertex, greater below; length 

 of visible portion of proboscis in both sexes about 0'75 mm. j 

 length of wing, ^ 6"G to 7*J) mm., ? 8*75 to 11 mm. 



