THE DIPT ERA 311 



pupae at or coming to the surface for air, and anj^ adults which may ahght 

 on the water to lay their eggs. Rain water barrels and cisterns for storing 

 water for use can be screened, and ponds where the use of oil is undesirable 

 may be stocked with small fish (sun-fish or top minnows) which feed 

 voraciously on these insects. Recent experiments indicate that where 

 the water must be used for drinking purposes, making the use of oil 

 objectionable, sprinkling powdered formalin on its surface will kill 

 mosquito larvae but not fish present, without making the water impossible 

 to drink! 



The catch-basins of sewer openings are usually favorite breeding places 

 for mosquitoes and these must be given attention, along with cess-pools 

 and any tin cans or other receptacles containing rain water which can be 

 found. 



Oil used should be sprayed on the water, working preferably along its 

 windward side and using about 1 fl. oz. to every 15 sq. ft. of surface. 

 The oil will spread if simply poured onto the water, but rather more of it 

 will be required by that method. It is important to be sure that little 

 detached pools along the shore receive their film of oil also. This treat- 

 ment should be repeated every 10 to 15 days unless heavy rains carry off 

 the oil soon after a treatment, in which case the oil should be renewed 

 sooner. Sawdust soaked in kerosene has been found to give up the oil 

 slowly and thereby preserve the film on the surface longer, when this 

 material is scattered along the edge of the water. 



Family Itonididae (The Gall INIidges). — These tiny flies are very 

 numerous. Most of them produce galls on plants, living in these galls, 

 but some suck plant juices without producing galls, and a few live in 

 decaying wood or fungi, or even feed on Aphids. The adults have long 

 antennae with, in the majority of the species, a whorl of hairs on each 

 segment. All parts of the plant are attacked by one species or another, 

 and the galls produced are typical for the species in each case. 



The gall appears to be the result of the irritation caused by the larva 

 feeding, and to some extent its size is dependent upon the number of 

 larvae present. Winter is frequently spent as the larva inside the gall 

 and, in manj'^ cases, there is but one generation each year though, on the 

 other hand, some species have several generations. 



The larvae are small, often ]:)rightly colored maggots. The method of 

 pupation varies in different species, some forming true cocoons while 

 others have a puparium and others are without any covering. 



Among the species not producing galls is the Clover-flower Midge (Dasyneura 

 leguminicola Lint.) which lays its eggs in the flower heads of mammoth, red, 

 crimson and white clover and is probably present everywhere in America where 

 these clovers occur. There are two generations each year. The larvse feed on 

 the flowers and prevent their forming seed. As the insects do not affect other 

 parts of the plant, they are not of serious importance except where seed is grown, 



