25 



Usinger: Introduction 



Intro, fig. 28. Sampling adult mosquitoes in a hollow trunk 

 of a tree (U.S.P.H.S., C.D.C. photo). 



sampling at a single station, properly chosen, can 

 provide valuable data from week to week and year to 

 year and is the best criterion we have for judging the 

 relative abundance of most mosquitoes. 



Intro, fig. 29. Anopheles mosquitoes resting on the ceiling of 

 barn. Inset — mosquito in biting position (U.S.P.H.S., C.D.C. 

 photo). 



Larval and pupal densities are in some ways easier 

 to determine. A standard, white enamel dipper is 

 commonly used as a sampler (intro. fig. 31). The 

 dipper is placed at the water surface and one edge 

 is tipped so that water flows in, carrying larvae and 

 pupae with it. Specimens can be seen, counted, and 

 collected with a pipette if necessary. Hess (1941) 

 devised a straight-edged screen dipper that samples 

 a standard area of surface, thus giving more meaning- 

 ful results but this dipper has not come into general 

 use. Dippers are totally inadequate under some circum- 

 stances. For example, the water in a weed-choked 

 Irrigated pasture is so shallow that other means must 

 oe used. As a partial solution to this dilemma Yama- 

 guchi (1949) devised a "sleeve sampler" consisting 

 of a vertical cylinder from which larvae were removed 

 oy a hand-operated suction pump (intro. fig. 32). A 

 standard number of dips or samples should be taken 



Intro, fig. 30. Red box serving as an artificial resting place fc 

 adult Anophelines (U.S.P.H.S., C.D.C. photo). 



and the counts recorded so that data will be compa- 

 rable. Only experience in a particular area can 

 determine at what level of adult or larval counts 

 control measures should be undertaken. 



Control measures. — The various methods used in 

 mosquito control are diverse and must be adapted to 

 each situation. For adults, which should be the last 

 line of defense, indoor space sprays are employed — 

 using aerosol "bombs" or even the simple "Flit>gun." 

 Aerosol mists and sprays are designed for quick 

 knockdown of mosquitoes and have been used for 

 this purpose even over extensive outdoor areas with 

 applications made by airplane or specialized equip- 

 ment on the ground. Most adult sprays contain DDT, 

 pyrethrum, or some other material which has a residual 

 effect when sprayed on walls or other surfaces. Resid- 

 ual sprays are particularly effective in malaria 

 control because engorged females of some Anophelines 

 rest on treated walls and are killed before thev are 



Intro, fig. 31. Sampling for mosquito larvae with a white enamel 

 dipper (U.S.P.H.S., C.D.C. photo). 



