402 MOSQUITOES OF NORTH AMERICA 



has visited the marshes, has seen the excellent results of the work accomplished, 

 and has watched the operation of digging the ditches. 



A bit of work, excellent in its results and very economical in its cost, in the 

 way of the drainage of an upland marsh, is described by Doctor Smith in his 

 report for 1908. A new normal school was about to be constructed on Montclair 

 Heights, and there were swampy areas nearby which a committee of the State 

 Board of Education considered to be dangerous as mosquito breeding-places. 

 Doctor Smith caused an inspection to be made early in April, and found that 

 there was a danger point in which not only the ordinary pool mosquitoes but 

 malarial mosquitoes could develop. At a cost of $250, three thousand feet of 

 ditching was placed or improved and all the surface water was drained to a 

 culvert through a railroad embankment. The heavy rains of May gave excellent 

 opportunity for testing the effectiveness of the work and no mosquito breeding 

 was found there throughout the season. 



THE PRACTICAL USE OF NATURAL ENEMIES OF MOSQUITOES. 



Almost no practical use has been made artificially of the natural enemies of 

 mosquitoes except with fish. It is true that about 1898 Mr. Albert Koebele im- 

 ported into Hawaii from California a large number of western salamanders 

 {Diemyctylus tortosus Esch.), which were liberated in the upper part of the 

 Makiki stream in the hope of reducing the large number of mosquitoes breeding 

 in small pools and in the taro fields. He kept two of these salamanders for 

 several weeks in an open tank and they devoured all mosquito larva that oc- 

 curred there; and while hundreds of the newly hatched mosquito larvae could 

 always be observed, none of them ever reached full growth. Whether these 

 salamanders have increased in Hawaii and at present form an element in mos- 

 quito control is not recorded. 



It has been suggested to breed mosquitoes of the genera Psorophora and 

 Megarhinus, the larvae of which are extremely voracious and feed upon the 

 larvse of other mosquitoes; but Psorophora itself in the adult condition is an 

 aggressive biter, so that to breed it for predaceous purposes is hardly to be con- 

 sidered ; in other words, the remedy might prove worse than the disease. How- 

 ever, Dr. Oswaldo Gongalves Cruz, Director-General of the Board of Health in 

 Eio de Janeiro, told one of the writers in November, 1907, while on a visit to 

 Washington, that Lutzia higotii is used in Eio to destroy the larvae of the yellow- 

 fever mosquito. The Lutzia larvae are exclusively predaceous, and this species 

 is introduced in regions where the yellow-fever mosquito abounds, and its larva3 

 destroy the other larvae. 



For a long time fish have been used practically on a small scale. For example : 



(( 



It was stated a number of years ago in Insect Life that mosquitoes were at 

 one time very abundant on the Eiviera in South Europe, and that one of the 

 English residents found that they bred abundantly in water tanks, and intro- 

 duced carp into the tanks for the purpose of destroying the larvae. It is said 

 that this was done with success, but the well-known food-habits of the carp seem 

 to indicate that there is something wrong with the story." (Mosquitoes, p. 161.) 



