HAEMATOPHAGOUS SPECIES OF MUSCA 349 



' flies '. It is obvious that this observer was not dealing with the house 

 fly but with haematophagous muscids. 



Up to the present time these muscids have attracted little or no atten- 

 tion, but it can be readily understood that they may act as the vectors of 

 parasites of all kinds. In describing a recent outbreak of Trypano- 

 somiasis (Murrina) among horses and mules in Panama, Darling pointed 

 out that the trypanosome w r as, in all probability, being transmitted by 

 flies of the genus Musca, which swarmed on the sick animals. A few- 

 days before death excoriated patches, which exuded trypanosome-con- 

 taining serum, formed on the necks, sides and heads of the diseased 

 animals ; the flies were attracted to these sores, and as they crawled over 

 them their legs and proboscides would naturally become infected. On 

 passing from a sick to a healthy animal they could readily infect the 

 latter when they insert their proboscides on the spots at which biting 

 flies had previously sucked blood. It is quite possible that the trypano- 

 some of Surra, for instance, is transmitted in this simple way, for there 

 is as yet no convincing proof that any biting fly acts as the invertebrate 

 host. 



These blood-sucking muscids are of interest to the dipterologist, for 

 they indicate the probable lines along which the true biting Muscidae 

 have evolved ; although their proboscides are structurally similar to those 

 of Group I, it is interesting to note that in some of them the prestomal 

 teeth are reduced in number. Short descriptions of all the known 

 species are given here. 



Musca pattoni, Austen. Male. Thorax, yellowish grey to bronze black, 

 with four broad black longitudinal stripes. Abdomen ochraceous buff 

 with silvery patches. First segment uniformly yellow with a short broad 

 median black longitudinal stripe. Second segment with a broad trian- 

 gular median black longitudinal stripe, a silvery patch on each side, and 

 a lateral brownish patch. Third segment with markings similar to those 

 of the second segment, except that the median longitudinal stripe is 

 narrower. Fourth segment dark, with an extremely narrow median 

 longitudinal stripe, and brown sides. Length 5'5 to 8'5 mm. 



Female (Plate XLV, fig. 1). Thorax, yellowish grey, with four longi- 

 tudinal bands, narrower and lighter in colour than in the male. Abdomen 

 with markings similar to those of the male, but the silvery patches at 

 the sides of the median stripe are more conspicuous, and the lateral 

 brown bands narrower. The fourth segment is brown with a dark apex. 

 Length 7 to 7'5 mm. 



In shape and general structure the egg of pattoni (Plate XLVI, fig. 2) 



