Studies on interspecies competition between the azuki bean weevil and the southern cowpea weevil

Abstract

SummaryExperimental studies was made on the interspecies competition between the azuki bean weevil, Callosobruchus chinensis and the southern cowpea weevil, C. macultatus. And the following results were obtained. The reverse result of competition between the two species observed under the air‐tight condition and the air‐free one. That is, the population of the azuki bean weevils destroyedby that of the southern cowpea weevils under the former condition and vice versa under the latter. It is thought that such a reversal is due to the difference of sensibility of each species to the air‐tight condition. Under the air‐free condition, change of the time interval of food‐supplying had no effect on the result of competition within the limits of this experiment. The population of the southern cowpea weevils was always destroyed by that of the azuki bean weevils. But there was a certain degree of correlation between the duration of co‐existence and the interval of food‐supplying. From the results, it is possible to say that by changing the degree of air‐tightness, or the time interval of food‐supplying, the co‐existence period and the final result of competition can be changed. The different mechanism of competition between two species in the present experiment from the experiments ofUtida (1952) andYoshida (1957) were discussed. A difference in the mechanism of interspecies competition and intraspecies competition was expected from the level of total population numbers of two species and the individual weight of C. chinensis.