EFFECTS of SOUND TRAPS on CAPTURE of CHIRONOMID MIDGES near a HYPER-EUTROPHIC LAKE in an URBAN AREA in JAPAN

Abstract:
In the area of Lake Suwa in central Japan, massive swarms of chironomid midges have repeatedly caused problems for local residents. Until now, light has been used as the customary countermeasure against chironomids wherever they occur, e.g., around natural lakes. In recent years, large numbers of swarming males of chironomid midges, Rheotanytarsus kyotoensis (Tokunaga) and Chironomus yoshimatsui (Martin et Sublette), were caught by traps emitting artificial wingbeat sounds. The present study was carried out to trap adult midges by wingbeat sounds in the field for the purpose of developing a new control method against these species using their acoustic response. Trials were conducted in 2000 from 30 May to 10 June (Chironomus (Lobochironomus) dissidensWalker), in 2000 from 2-5 June (emergence period of Chironomus plumosus (L.); summer generations) and in 2000 from 16 October to 6 November ( Propsilocerus akamusi (Tokunaga)). A speaker connected to a cassette tape recorder was placed in the center of a cylinder of transparent polyethylene. Glue was sprayed on the inside wall of the cylinder. The sticky area was about 900 cm2. Two cylindrical traps, one emitting sound and the other not, were set in parallel about 30 cm apart. The traps were placed in the vicinity of swarm. Sinusoidal sounds at various frequencies recorded from a sound generator were emitted at intervals of 10 s on/5 s off for 2 min by a cassette tape recorder. The sound intensity was kept at 90-dB sound pressure level at the cylinder edge. Most swarming males ofC. dissidens were caught by cylindrical sound traps emitting a sound frequency of 240 HZ at 20.5±3.1oC , and C. plumosus were caught by 270 Hz (range 240-300) at 17.6±1.2oC On the other hand, P. akamusi were caught by 165 (150-180) Hz at 14.6±1.2oC. It is concluded that the most attractive frequency differed among species according to air temperature.