Abstract
Few studies have been conducted on the biology of chironomid midges occurring in rice paddies, albeit their occurrence in significant number and biomass. This investigation was made for three years from 1977 to 1979 in four paddy plots at 50-km north of Tokyo, which were treated with three different fertilizers and with none. The organic fertilizer plot produced 1,765 midges per square meter per season, followed by the inorganic fertilizer plot producing 1,376. About half numbers were produced in the non-fertilizer and green manure plots. Fifteen species occurred from these paddies. Chironomus kiensis, Tanytarsus sp., Microtendipes sp. and Procladius crassinervis were most abundant in this order. Simpson's diversity index tended to be small at the beginning of the season but became large as it progressed. No spray of agricultural chemicals reduced the chironomid populations appreciably but mid-season drainage did. A significant correlation was obtained between chironomid population size and β-glucosidase activity in soil when 15 physical, chemical and biological characteristics were correlated. Rice leaf cover and phosphate ion concentration were also inversely correlated with the population size.
