AQUATIC MIDGES AND SOME RELATED INSECTS. 1 7 



yet there is no doubt whatever that the two species will be found to resemble each other 

 very closely, as it is difficult to find any satisfactory distinctions between them from 

 their descriptions. 



Group II.— Tanytarsus pusio Meigen. 



For this group Tanytarsus pusio Meigen has been selected as a type, because Mundy 

 (1909) has already studied it so completely that there is relatively little new material 

 to be added. The only larva whose feeding habits he describes is the species given 

 above, but he designates "Larva No. 1 " and apparently "Larva No. 18" as also feeding 

 in a similar manner. "Larva No. 18," he says, "builds a still more elaborate case, 

 composed of long stalks to which is attached a short tube with three long arms given 

 off at the free end. The case is not quite so opaque as that of T. pusio and is of a light 

 biown color." The author has bred T. exiguus from similar tubes and observed its 

 habits, which resemble very closely those of T. pusio, as described by Mundy. 



CONSTRUCTION OF TUBE. 



The following description is taken from Mundy's work (1909). The latter part is 

 condensed from a more complete description. 



The first thing the larva does is to gather a number of particles of mud together and form them into 

 a short strap or band passing across the body and fixed to the dish on each side. Using this band as a 

 starting point the larva sets about building a simple straight tube closely applied to the dish and open 

 at both ends. At first the band is merely broadened so as to cover more of the body, but soon it is 

 shortened as well until length and breadth change places and a real tube is formed. * *. 



Anchored, as it were, to the strap by its anal feet it rapidly sweeps through an angle of about 6o°, 

 touching the surface here and there with its mouth as it passes. Then, firmly grasping a particle by 

 means of the labial armament and the anterior appendages, it powerfully contracts its body, thus 

 drawing the particles toward the centre of operations; but not only do the above mentioned particles 

 move, but all those touched during the sweeping movement follow in its wake, having been united 

 together by silk threads or mucus during the first action. In this way abundance of material is col- 

 lected and the building of the case proceeds rapidly. 



According to Mundy (1909) Tanytarsus pusio and "Larva No. 1," which builds a 

 stalk case, begin their tubes and construct them to a large extent exactly alike. When 

 the tube of " No. 1" is 3 millimeters long, it begins to build it up horizontally, removing 

 material from the opposite end of the old tube for this purpose. This is carried on 

 until there is only a narrow stalk projecting up from one side of the original burrow 

 supporting on its top end a short tube. This tube is later strengthened by the addition 

 of saliva especially at the attachment. Then three arms are provided and the web 

 attached. 



In strengthening an arm the larva twists its head right around it, describing thereby a complete 

 circle, completing the forward and return movements with the greatest rapidity. [Mundy, 1909.] 



Tanytarsus pusio makes a dark-brown mud tube fastened together with saliva 



but not lined with a distinct silk lining. 



The tube is attached for a variable length to rock or moss stem in the bed of a river, but it grad- 

 ually curves away from its support, so that the anterior end projects freely in the water. This end is 

 the widest, from which it gradually tapers toward the base. 



