Studies on the population dynamics of a thistle‐feeding lady beetle, <i>Henosepilachna pustulosa</i> (<scp>Kôno</scp>) in a cool temperature climax forest

Abstract

Summary A field study was carried out on the population dynamics of a thistle‐feeding lady beetle, Henosepilachna pustulosa ( Kôno ) living in a cool temperature climax forest in northern Kyoto Prefecture, central Japan. Intensive marking, release and recapture program was carried out to estimate the adult population parameters by using Jolly‐Seber method. Sampling ratio was around 50%. Marking ratio rapidly rised as the census progressed and approached to 100%. Sex ratio (% ♀) was 63–69% in both overwintered and new adults. Daily survival rate was as high as 0.95 or more and constant throughout the season. Adult longevity in the spring was longer than 40 days. Reproductive rate i. e., the ratio of the number of newly emerged adults in a given generation to that of overwintered adults in the preceding generation, is very small, ranging 1–3, whereas winter survival is higher than 50%, consequently the size of populations in the study area remain in a remarkably constant size and it never reached a level where intraspesific competition occurred. The population characteristics of H. pustulosa are compared with those of the two closely related species, H. vigintioctopunctata and H. vigintioctomaculata , which are the pests of Solanaceous crops. Hp is more K ‐strategic than the two pest species.