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Swarming and Some Other Habits of Mansonia Perturbans and Psorophora Ferox (Diptera: Culicidae)

1964; Brill; Volume: 24; Issue: 1-2 Linguagem: Inglês

10.1163/156853964x00229

1568-539X

Hedvig Tetens Nielsen,

Malaria Research and Control

[Observations on the swarming of Mansonia perturbans and Psorophora ferox have been made. M. perturbans swarmed over contrasting areas of white and dark colors. The swarms began near the end of twilight, at +0.80 crep, and continued to +1.87 crep. On rainy and windy occasions the swarms were very small and lasted 0.82 crep. In windy and clear weather, and on calm and cloudy days they lasted 0.58 and 0.80 crep respectively, compared to 1.28-1.32 crep on clear days with little or no wind. During a pre-swarming flight (ascent) the mosquitoes spread out over a rather large area with flight movements of large amplitude. The duration of the ascent was shorter at high temperatures than it was at low temperatures. There was a positive correlation between duration of swarming and number of participants. During windy weather the mosquitoes did not react to noises, as they did in calm weather when they were attracted to notes ranging from 240-300 vibrations per second. Three broods of Psorophora ferox were ohserved. Common to all three broods was the peculiar habit of daytime swarming, which occurred at any hour of the day whenever the sun was obscured by clouds and the light intensity fell below 4.0 log lux. The lower the light intensity in the more individuals took part in the swarming. Also, the heavier the cloud the longer the swarm lasted after the cloud had passed. These daytime swarms seem comparable to the ascent seen in other species: Aedes cantans (NIELSEN & GREVE 1950) and Aedes caspius (NIELSEN & NIELSEN 1958) though these latter species were confined to a period immediately before the crepuscular swarming. Towards sunset when the light fell below 3.0 log lux the swarming became continuous with a maximum number of participants. Temperature below 20° appeared to influence Ps. ferox in several ways: 1. The antennal fibrillae which were permanently extended at high temperatures were extended only during the swarming in February when the temperatures were below 20° most of the time. 2. Instead of beginning to swarm the day after emergence as they did in September and October they did not begin until four days after emergence during the February observations. 3. When the swarms were established during the February observations a drop in temperature from 27° to 15° did not influence the swarming but low temperatures before swarming had commenced inhibited the swarming until the temperature rose above 21°. Matings and attempted matings occurred in the morning and forenoon often in the provoked swarms, rarely in small swarms after these were established, never in the twilight swarms. Feeding was observed during the cold period but only once during the October observations. Daytime resting places were found and observed but nighttime resting places were never seen., Observations on the swarming of Mansonia perturbans and Psorophora ferox have been made. M. perturbans swarmed over contrasting areas of white and dark colors. The swarms began near the end of twilight, at +0.80 crep, and continued to +1.87 crep. On rainy and windy occasions the swarms were very small and lasted 0.82 crep. In windy and clear weather, and on calm and cloudy days they lasted 0.58 and 0.80 crep respectively, compared to 1.28-1.32 crep on clear days with little or no wind. During a pre-swarming flight (ascent) the mosquitoes spread out over a rather large area with flight movements of large amplitude. The duration of the ascent was shorter at high temperatures than it was at low temperatures. There was a positive correlation between duration of swarming and number of participants. During windy weather the mosquitoes did not react to noises, as they did in calm weather when they were attracted to notes ranging from 240-300 vibrations per second. Three broods of Psorophora ferox were ohserved. Common to all three broods was the peculiar habit of daytime swarming, which occurred at any hour of the day whenever the sun was obscured by clouds and the light intensity fell below 4.0 log lux. The lower the light intensity in the more individuals took part in the swarming. Also, the heavier the cloud the longer the swarm lasted after the cloud had passed. These daytime swarms seem comparable to the ascent seen in other species: Aedes cantans (NIELSEN & GREVE 1950) and Aedes caspius (NIELSEN & NIELSEN 1958) though these latter species were confined to a period immediately before the crepuscular swarming. Towards sunset when the light fell below 3.0 log lux the swarming became continuous with a maximum number of participants. Temperature below 20° appeared to influence Ps. ferox in several ways: 1. The antennal fibrillae which were permanently extended at high temperatures were extended only during the swarming in February when the temperatures were below 20° most of the time. 2. Instead of beginning to swarm the day after emergence as they did in September and October they did not begin until four days after emergence during the February observations. 3. When the swarms were established during the February observations a drop in temperature from 27° to 15° did not influence the swarming but low temperatures before swarming had commenced inhibited the swarming until the temperature rose above 21°. Matings and attempted matings occurred in the morning and forenoon often in the provoked swarms, rarely in small swarms after these were established, never in the twilight swarms. Feeding was observed during the cold period but only once during the October observations. Daytime resting places were found and observed but nighttime resting places were never seen.]