AQUATIC MIDGES AND SOME RELATED INSECTS. 29 



stomach is allowed to become more than half empty, and often the larva resumes its 

 feeding operations when the stomach is practically full. 



An attempt was made to determine the length of time that the food remained in 

 the alimentary canal, but the small size of the larvse and the acute discrimination in 

 their feeding habits prevented the use of any coloring substances to mark any portion 

 of their food. Direct observation was resorted to but proved too tedious to afford accurate 

 data. The larvae often withdraw from the end of their burrows and remain almost 

 motionless for an hour or so at a time. Then they will begin feeding again, working 

 for a half or three quarters of an hour at a time with only occasional short intermissions 

 for the purpose of renewing their air supply by setting the water in circulation. By 

 noting the intervals between feeding and resting it seems doubtful if the food remains 

 in the body for more than two hours. 



There is no special masticating apparatus present, and the result is that a very 

 large per cent of the parenchymatous cells swallowed pass through the body entirely 

 unaltered. The use of the castings for roofing material in connection with the burrow 

 places these cells in a position which, while artificial, nevertheless offers conditions 

 under which the carrying on of their life processes should be partially possible. These 

 cells are held suspended in a silken mesh, bathed in water rich in the mineral salts, 

 resulting from the digestion of similar cells, and favorably placed for the obtaining of 

 carbon dioxide. That the covering of a larval burrow remains green for a considerable 

 time is readily observed, and it seems possible that the larvae have in this matter hit 

 upon a favorable adaptation. 



ECONOMIC IMPORTANCE. 



The aquatic conditions of life required by Chironomus brasenia; larva? confine their 

 attacks to leaves at or beneath the surface where their burrows may be flooded with 

 water. This requirement limits their attacks to a restricted variety of plants. The 

 writer's observations on the injury done aquatic plants by C. brasenice are confined to 

 the one place where they occur within a reasonable distance of Ithaca, N. Y., which is 

 Spencer Lake. Here the conditions seem to be excellently adapted to the growth of 

 aquatic plants. The lake is shallow and Brasenia schrebcri is the dominant plant with 

 floating leaves, while Castalia ordorata is present in various parts of the lake and is next 

 in abundance. Observations made on July 22 show a very considerable proportion 

 of the leaves of Brasenia infested, while only one or two doubtful cases of the infestation 

 of Castalia were observed. On October 7 the entire pond was examined, and a leaf of 

 Brasenia which had not been injured by this larva was so rare as to make it difficult 

 to explain how it escaped. The leaves of Castalia showed a greater percentage of 

 infestation later in the season than at the time of the author's earlier visit, but they 

 were not badly injured. Dr. Pettit says of the damage to water lilies: 



The pads of both Nuphar advena and of Nymphea odorata were furrowed by some miner. The 

 pads had been badly eaten in some places and many contained living larvae and pupae. 



CONTROL. 



The injury done by these larvae in parks and private gardens may some time become 

 so great that methods of control will be necessary. At first thought it would not seem 

 feasible to spray for an aquatic larva, but, as shown above, the water is kept circulating 



