Showing papers in "Applied Entomology and Zoology in 1980"

Seasonal Changes of the Proportions of Mated Females in the Field Population of the Rice Leaf Roller, Cnaphalocrocis medinalis GUENEE (Lepidoptera : Pyralidae)

Abstract: the rice leaf rerler, Cnaphalecroeis medinalis Guenee, collected from fields and by light trap in 1977 and 1978, It became crear that the proportions of the mated females fluctuated extremely by season. Most of the females collected in the paddy fields mated from ,June to early September. Thereafter, the proportions of mated females declined greatly up to mid-October, when almost all female moths contained immature ovaries and abundant fat body in their abdornens. From late October threugh the rest of the season the mated females, rnost of which leoked lean, increased considerably in number. Some difi'erence of the reproductive conditions was also neted among the three kinds of sarnples : female moths collected in the paddy fields, in the grassy fields and those captured by Iight trap. Some possible causes for the disappearance of the mated females in autumn are discussed.

Host-finding behavior of the rice bug, Leptocorisa chinensis Dallas (Hemiptera: Coreidae), with special reference to diel patterns of aggregation and feeding on rice plant.

Abstract: periment to elucidate its host-finding behavior, Adult bugs were observed to feed in daytime and fly actively after sunset. Flight tunnel experiments in daytime showed their upwind orientation to the odour source of rice plants, though the response was not so high as to explain the aggregation of thc rice bug on the ricc plant in the flowering stage. It is postulated that the rice bug can detect the odour of rice plants in close to the rice field, but the aggregation on the ears of rice plants scemed to be caused mostly by the arresting efflect of the eaTs in the flowering stage.

Mating behavior of the rice stem borer moth, Chilo suppressalis Walker (Lepidoptera: Pyralidae). IV. Threshold-light-intensity for mating initiation under various temperatures.

Abstract: The eflects of light-intensity and temperature on mating of thc rice stem borer moth, Chito stEApressalis Walker, were investigated, The threshold-light-intensity for mating initiation varies with temperaturc. At as high a temperature as 30\"C, mating was inhibited by a feeble light greater than 5 Iux, but the threshold-light-intensity for mating initiation shifted higher rapidly with decreasing temperature, such as ca, 65 Iux at 250C, ca. I80 lux at 200C, ca. 600 lux at 150C. Also, mating was initiated by decrease of temperature within certain resnicted light-intensity without light-off stimulation. This phenornenon seems te be evidence for the previous description that the threshold-light-intensity for mating initiation is varied by ternperzture, Thcse results suggest that one of the reasons of the seasDnal variation of mating tirne is attributed to changing sensitivity of moths to light according to temperature to which they are cxposed,