150 MISC. PUBLICATION 631, U. S. DEPT. OF AGRICULTURE 



more or less hairy, but never with hair that is squamose ; the humeri 

 are pilose. Vein r 4+5 curves strongly into the middle of the apical 

 cell ; the marginal cell is closed and petiolated. 



Larvae. — The larva (fig. 90) is the familiar rat-tailed maggot; but 

 all rat-tailed larvae do not, by any means, belong to this genus. The 

 assumption that all such larvae are T. tenax is undoubtedly responsible 

 for many incorrect records and inaccurate descriptions. 



The "rat-tail," or respiratory tube, consists of 3 segments; when 

 contracted, the second and third are telescoped into the first, so that 

 the second is entirely concealed and only the tip of the third shows. 

 When fully distended, in the mature larva, the respiratory tube is 



Figure 90. — A, Larva of Tubifera, side view; B, same, dorsal view; C, same, 

 tracheal trunk; D, larva of Helophilus, tracheal trunk. (After Johannsen, 

 61, pi. IV).) 



at least twice, and usually several times, the length of the body. The 

 body is more or less cylindrical and is pilose ; the abdominal segments 

 lack the lateral lobes found in some genera of Tubiferinae; the tra- 

 cheal trunks (fig. 90, G) are straight; the anal gills, 9 to 20 in number. 



Pathogenesis. — A number of seemingly authentic cases of gastro- 

 intestinal myiasis have been recorded. An unidentified species of 

 Tubifera has been removed from the nose of a patient, and vaginal 

 myiasis has been reported in cattle. 



Literature. — The Palaearctic species have been treated in Lindner's 

 "Die Fliegen der Palaearktischen Region." For a key to the New 

 World species, see Curran (#£, p. 3-7) , and for a discussion of the im- 

 mature stages, Johannsen (62, pp. 25-26). 



