Distribution of the mosquitoes, Culex tritaeniorhynchus, in relation to disposition of sound traps in a paddy field

Abstract

The spatial and temporal distributions of Culex tritaeniorhynchus were studied with sound traps at an unisolated 1.7 ha area of a paddy field in Chikugo City from Jul. 23 to Aug. 4. Fourteen traps were placed on black cloth swarm markers at 20-50m distance from each other, and a 370Hz, 100 or 110dB sound was emitted for 20min during the swarming time, 19 : 42 to 20 : 02. As the results, 20,141 males and 1,116 females in total were caught. There was a sex-biased spatial distribution; males evenly distributed over the breeding paddy, but some males nightly migrated out to a pigpen nearby. The females, on the contrary, took the host appetent flight and heavily concentrated in the vicinity to the pigpen. The significant reduction of blood-fed females trapped and resting in vegetation was observed towards the end of experiment. This reduction would be attributed to the decreased emergence of mosquitoes due to the mid-season water drainage in the paddy or the increased rates of virgin females due to the possible mating disruption by sound, or both.