38 Bulletin No. 159 



drical, dull-gray grubs, with a rather small head more or 

 less completely withdrawn and concealed in the first body 

 segment. The body is deeply and simply wrinkled, each 

 division with a few short erect black hairs, in pairs. 

 Obscure tubercular prominences become more pronounced 

 on the ventral sides of the somites, the last one of which 

 bears three pairs of fleshy, unjointed, dusky appendages, as 

 follows : A pair of short ones on the dorsal side; a pair of 

 longer ones, one on each side of the dorsal pair, with a tuft 

 of black hairs at the tip of each and a couple of small tuber- 

 cular offshoots; a third still longer pair projecting down- 

 ward and backward, each bearing a tuft of radiating black 

 hairs at the tip and with two small tubercles. A pair of 

 eye-like structures is conspicuous at the back of the short 

 dorsal pair of appendages. The under side of the posterior 

 somite bears six soft contorted appendages. Length of 

 largest example 20 mm. 



TABANID/E (GADFLIES). 



Tabanus sp. — A larva of one of these stinging flies was 

 taken in the Left Fork of Straight Creek near a dwelling 

 occupied by people suffering with pellagra. The strong- 

 flying adults produced from such grubs are known as gad 

 flies, and are common pests of stock, attacking especially 

 horses and cattle, but not neglecting even hogs, and now 

 and then venturing upon man himself. The young have 

 sharp puncturing mouth-parts with which they destroy 

 snails and other aquatic animals upon which they feed, 

 They are found in mud and among vegetable refuse at the 

 bottom, commonly, and being without limbs move by a 

 wriggling motion, but when dislodged swim to some pur- 

 pose though rather awkwardly. 



It is not likely that they will prove to have anything to 

 do with pellagra, though the strong beaks of the flies are 

 efficient instruments for puncturing the tough and thick 

 skins of cattle, and might easily serve to convey the virus 

 of diseases. Fortunately they are not commonly disposed 

 to attack us. 



