16 N. H. AGRI. EXPERIMENT STATION [Bulletin 243 



FISH 



Artificial ponds, and natural ponds and lakes, if necessary, should be 

 stocked with fish which will eat the larvae and pupae of mosquitoes. The 

 common goldfish, the silverfish, the fresh-water killifishes, and the top 

 minnows are all useful in stocking water that contains no fish. Natural 

 waters are usually well stocked with various species of fish which will 

 feed on the mosquitoes. In any case it is necessary to clear out the veg- 

 etation-choked margins and eliminate or open up isolated pools so that 

 the fish will have free access to all parts of the pond. This treatment is 

 all that is necessary for mosquito control in ponds and lakes if they do 

 not have swamps in connection with them. 



SCREENING 



Screening houses will exclude most mosquitoes, but must be done 

 thoroughly as these insects are able to enter through very small cracks. 



Screens for doors and windows should be made to fit tightly, and the 

 wire should have not less than sixteen meshes to the inch. In some parts 

 of the country beds are provided with canopies of mosquito netting and 

 these are often used in camping. The netting should be free of tears 

 or expanded meshes and large enough so that it can be tucked well under 

 the mattress. Headnets are sometimes worn when fishing or working 

 where mosquitoes are very numerous. 



REPELLENTS 



Many preparations are on the market, ad\ertised as mosquito repel- 

 lents. Most of them contain some volatile oil, such as oil of citronella, 

 oil of pennyroyal, or cedar oil. These will helj) to keep mosquitoes away 

 for a time, but an application is not effective for more than an hour or 

 so. Kerosene extracts of pja-ethrum may be used in the same way, and 

 these are also useful as a spray in killing mosquitoes in the house. For 

 the latter purpose, the room should be closed tightly and the material 

 applied with a good atomizer. The walls and ceiling should be cov- 

 ered, the air should be filled with the mist, and special attention should 

 be given to hiding places, such as closets and beneath furniture. The 

 rooms should be kept closed for some time after the treatment. 



LIST OF SPECIES 



The following list includes all the mosquitoes known to occur in New 

 Hampshire, together with a few that will certainly be found with addi- 

 tional collecting. The general statements made under the genus are char- 

 acteristics common to all, or nearly all, the species of that genus. Addi- 

 tional information or exceptions to the general statements are given 

 under each species. When a genus has only one representative in the 

 state, all the information is placed under the species. 



