Studies on the Bionomcis of the Rice Stink-bug, Lagynotomus assimulans DISTANT
VI. The Influences of Climatic Factors on the Crawling Activity of Adults
1959 Volume 3 Issue 1 Pages 7-15
Details
1959 Volume 3 Issue 1 Pages 7-15
The influences of air temperature and relative humidity on the crawling activity were studied at intervals of 2 hours from 5 to 23 in the summer of 1951, and also the influence of light intensity was observed at sunrise, sunset and during the daytime at intervals of 1 or 2 hours in the summer of 1957.
1. The rate of crawling activity was expressed by the percentage of crawling insects at each inspection time. During the hours from 5 to 17, the rate of crawling activity varied from 0 to 60% with averages of 14.0% in male and 8.6% in female. And from 19 to 23, under the illumination of a lamp, the above rate varied from 0 to 100% with averages of 52.4% in male and 46.1% in female. In the former, the relative frequencies of the rate lower than 30% were 84% in male and 95% in female. In the latter, the relative frequencies of the rate from 30 to 90% were 75% in both sexes.
2. The influence of varying intensity of light on the crawling activity is observed at intensities lower than 0.5lux before sunrise and lower than 30.0lux at sunset and during the former half of the night. The peaks of the rate of crawling activity appeares about one hour before sunrise at intensities below 0.5lux, immediately after sunset at 2.0lux and below, and presumably at a certain later time at much lower intensities than the former. And these peaks are considered to occur as the results of light-adaptation and dark-adaptation respectively. In the daytime, even a high intensity as 84, 000lux did not suppress activity absolutely and remarkable change in intensity did not affect the rate of crawling activity. But as the rate of crawling activity was lower than that of night and all the inactive insects began to crawl when the intensity was dropped from 800lux to 2 and 15lux, the intensity of light in the daytime seems to suppress the crawling activity to some extent.
3. In winter, adults begin normal crawling at a room temperature of about 16°C in the daytime. In summer, however, the range of normal crawling activity lie between the temperatures of about 22°C and 30°C in paddy fields. The rate of crawling activity increases as air temperature rises up to 26∼27°C from 9 to 13 and up to 27∼28°C from 15 to 17 respectively. These air temperatures are considered as the optimums. And above these temperatures, the rate of crawling activity decreases with the rise of temperature. The coefficients of correlation between crawling activity and air temperature varies with the lapse of time. They are higher from 9 to 15 below the optimums, showing values from 0.81 to 0.95 in male and 0.88 to 0.99 in female, and lower during the other times, especially at night. From 9 to 15, the air temperature rises up higher than the optimum and becomes negative showing highest values at 13 in both sexes. The variability of the optimum air temperature is supposed to be caused by the difference between the temperature of insect body and that of air, which is greater in the morning than in the afternoon.
4. From 7 to 23, the coefficients of correlation between crawling activity and relative humidity are negative and low varying with the lapse of time from 0.61 to 0.76 in male and from 0.53 to 0.66 in female. They are relatively higher from 7 to 11. From 7 to 19, air temperatures are more influencial than relative humidities on the crawling activity. But from 19 to 23 the case becomes reverse. At 5 or 7, the higher relative humidity above 90% seems to inhibit crawling activity to some extent.
