394 



(4) Genus Stomoxys. (a) Palpi very small, bear- 

 ing some hairs ; not projecting beyond the epistome. 

 (b) Proboscis is bent at its base like an elbow joint. 

 (<:) Arista plumose dorsally, distally forms a fine hair. 

 (d) Third and fourth long veins reach the apex. The 

 fourth is bent beyond the posterior cross vein. Wings 

 diverge widely. 



S. calcitrans. The ' stable ' fly, is common about 

 farm yards. 



Fig. 125. Stomoxys, shewing resting position 

 of Wings, x 2. (After Austen) 



Structure of Proboscis. In Stomoxys calcitrans as 

 in Glossina the cutting mechanism of the proboscis 

 lies in the labella. The structure of these is even 

 more complex than in Glossina, but consists essentially 

 of five very strong teeth on each side. These can be 

 completely everted and by rotation of the proboscis 

 tear through the skin. The proboscis proper consists 

 of (a) labrum, (b) labium, and (c) hypopharynx. The 

 relationship of these parts is shewn in the figure. 



(5) Genus Glossina (tsetse-flies).* Abdomen 

 generally, but not always, has pale but well-marked 

 dark-brown bands interrupted in the middle. 



* The data of this section are compiled from A Monograph of the Tsetse Flies, 

 by E. E. Austen, and from an article in the British Medical Journal, September 17, 

 1904, by E. E. Austen. 



