Chronomids (Diptera: Chironomidae) Attracted To Vending Machines in the Middle Reaches of the Shinano River, Japan

Abstract:
The species composition and abundance of chironomid midges attracted to the illuminated showcase of a vending machine, set on the riverside in the middle reaches of the Shinano River (Ueda City, Nagano Prefecture, Japan), were investigated. A total of 4,439 midges (1,719 males and 2,720 females) were collected on the showcase of the machine (110 × 85 cm2) for 20 minutes a day beginning at 20:00, everyday from March 28 to December 1, 2006. Males were identified as belonging to 92 species, of which the three most abundant were Chironomus kiiensis (379 males and 125 females: 11.4%), Polypedilum nubifer (236 males and 372 females: 13.7%) and Smittia aterrima (184 males and 254 females: 9.9%), accounting for 34.9% of the total Chironomidae abundance. The daily total Chironomidae abundance showed the highest peak in late August and showed the maximum attraction of 215.0 ind./20 min./m2 (201 ind./20 min./110 × 85 cm2) on August 23. C. kiiensis was collected from late June to mid-September, and its daily abundance was highest in late August. P. nubifer was collected from late June to late September and its daily abundance showed two distinct peaks, the earlier one in mid-July and the later one in late August. S. aterrima was collected from mid-September to early December, the end of the study period, and was abundant in November. Daily abundances of total Chironomidae, C. kiiensis and P. nubifer showed significant positive correlations with daily mean air temperature, whereas S. aterrima showed a significant negative correlation.