The mosquitoes used came from a variety of sources, ranging from long-established laboratory colonies to wild-caught specimens, and the details are given in the section on each individual species.

The recording method was developed from that first described by Jones (1964) and full technical details can be found in the author's dissertation (Taylor 1969a).

Essentially, the sound produced by the wing-beat of the flying mosquito was amplified and converted to an electrical impulse that triggered a relay switch in an event recorder. The resulting trace on a waxed-paper roll was scored, on the basis of 1 for activity in any single minute, and transcribed to results sheets as the activity score per half-hour (i.e. maximum score 30). From the scores, the mean activity of several individuals was calculated and plotted graphically as bar-charts of activity against time.

The experiments were conducted in conditions of constant temperature, 25°C unless otherwise indicated, and under LD regimes with 70 lux light, produced by two 15W tungsten bulbs, and complete darkness. The light-dark transitions were abrupt, with no use of simulated dawn or dusk; other authors have used gradual transitions but these have shown no great differences from abrupt transitions; for example, Ae. aegypti (Rowland & Lindsay, 1986), An. stephensi (Rowland, 1991) and Cx. p. quinquefasciatus (Jones & Gubbins, 1978, 1979). The lights produced a slight temperature increase, rising to 26° C by the end of 12h light and 27°C in LL. The LD regimes mostly were run with the photophase during natural day-time. Changes in regime, e.g. LD 12:12 to LD 16:8, were made by altering the time of light-on. When wild-caught British species were recorded the light-off approximated to the natural sunset on the date of capture, this is indicated in the species sections. Otherwise light-off was at 1800h.

Each mosquito was housed in a separate recording chamber and was provided with a tube of sugar solution, with a cotton-wool wick, and a tube of water. This was found essential for the longer-term survival of the mosquitoes, perhaps because it maintained an RH of 85-90%. Six or nine recording chambers were housed in each of the sound-proof boxes used for individual LD regimes.

The details given in the individual species sections show that, for logistic reasons, some experiments involved recording in an initial LD regime and then making a change. Usually, this was by altering the time of light-on by no more than 4h (e.g. LD 12:12 to LD 16:8). As it was found that such resetting rarely required more than one complete 24h LD-cycle to achieve a stable new pattern, the results from each regime are presented separately. The great majority of the graphs of activity show three consecutive 24h LD-cycles. The reader's attention is drawn to the fact that some graphs show only two 24h LD-cycles and to the fact that the Y-axes (giving activity score) vary from graph to graph according to the amplitude of the actual activity. This does, however, have the benefit of enabling the patterns of activity to be seen more easily when the amplitude is low. All the graphs are drawn with 0000h as the time of light-on and, as far as possible, figures with multiple graphs have light-on vertically aligned.

In interpreting the results, the convention of Pittendrigh & Daan (1976), with additions by Jones & Gubbins (1979), has been followed to designate the observed peaks of activity:-

E = evening, dusk. M = morning, dawn. N = night, midnight.

©1998, 2010 - Brian Taylor CBiol FSB FRES 11, Grazingfield, Wilford, Nottingham, NG11 7FN, U.K. Comments to dr.b.taylor@ntlworld.com

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