This method has been used in studies on the effect of residual insecticides on house resting mosquitoes (Smith 1964), in studies of hibernating
mosquitoes, and in other investigations of mosquito resting habits. The
mosquitoes resting on the walls and roof of a hut are carefully counted
but not caught, so that both the behaviour of the mosquitoes and the toxicity of the insecticide can be assessed. However, in East Africa Smith
(1964) found that in situcounting was actually only able to record about
47 and 61% of the total Anopheles gambiaepopulation resting in grass
and mud-roofed huts, respectively. When directly counting resting mosquitoes it is important not to disturb them, causing them to resettle elsewhere and potentially resulting in double-counting. Hibernating females
are more easily counted than non-hibernating mosquitoes as they are not
so readily disturbed. Weekly counts have been made of hibernating
populations of Culex pipiensand/or Culiseta annulatain England in
brick-built shelters (Service 1969; Sulaiman and Service 1983) and caves