Studies of the Biting-habits of African Mosquitos. An Appraisal of Methods employed, with special Reference to the twenty-four-hour Catch

Abstract

It is felt that the 24-hour catch presents a valuable method of studying the biting-behaviour of mosquitos in the field, and further that conclusions concerning seasonal abundance, vertical distribution and times of biting-activity must be based on catches of this type if serious errors of interpretation are to be avoided.The time-divisions of the catch should not exceed one hour, and even shorter intervals may be desirable. Timing should be related to the actual times of sunrise and sunset. Where possible, a series of consecutive catches should be carried out, and a shift system must be carefully considered in relation to the particular series projected.Usually the results from different levels above ground should be treated separately in working out biting-cycles, and this may also apply to results from different seasons or different localities. Further, while in some instances the summation of long series of catches seems permissible, in others it is not, and in these detailed analysis of the figures may be necessary before consistent behaviour-patterns become apparent.In cases where a measure of the central tendency is to be employed, the geometric mean as modified by C. B. Williams appears to be the most suitable.

Mosquito Frequency and Feeding Habits in an Enzootic Canine Dirofilariasis Area in Niterói, State of Rio de Janeiro, Brazil

“…The frequency distribution was used to analyze the discrete data, the Z test was used to compare two proportions (Rodrigues 1993) and the Williams' mean to analyze serial data (Williams 1937, Haddow 1954, 1960.…”

Sampling Adults by Animal Bait Catches and by Animal-Baited Traps

“…In England, however, Renshaw (1991) believed the high initial catch of Aedes can tans was due to hungry females following her through a wood to the catch site. Another characteristic of some bait catches is that adults may arrive in waves (Haddow, 1954;Service, 1969a), that is the sudden appearance of several individuals followed by short periods when few or no individuals arrive. This is possibly explained by slight changes in the drift of host odours causing the simultaneous stimulation of small groups of resting mosquitoes, which then arrive at the bait more or less together.…”

“…Such correlations may be difficult because these times alter according to both locality and season. The importance of adjusting catch times in relation to exact times of sunset and sunrise was stressed by Lumsden (1952Lumsden ( , 1957a and Haddow (1954 Haddow, 1956b) richiardii were an hour earlier and later than during July (Service, 1969a), cOrresponding to the new times respectively of sunset and sunrise. Another difficulty is that away from the equator day length varies and consequently it is difficult to adjust the catch clock to times of both sunset and sunrise.…”

“…Some species, e.g. Aedes ingrami, Aedes africanus, Coquillettidia aurites, Coquillettidia pseudoconopas, have been shown to exhibit pronounced daily vertical migrations within the forest (Germain et al, 1972(Germain et al, , 1973Haddow, 1954Haddow, , 1961aHaddow & Ssenkubuge, 1965;Mattingly, 1949a). The percentage biting at different levels can vary according to time.…”

“…A detailed appraisal of the 24-hr catch technique, which has been widely adopted though sometimes with modification, is given by Haddow (1954). Cheong et al (1988) provide a good example of 24-hr bait catches undertaken in Malaysia, in which at least 13 culicine species were collected.…”