Prediction of the life cycle of the west Japan type yellow-spotted longicorn beetle, Psacothea hilaris (Coleoptera: Cerambycidae) by numerical simulations

Abstract

A temporally structured model that enables simulation of the development of the west Japan type yellow-spotted longicorn beetle, Psacothea hilaris (Pascoe), at different locations was developed. Life history parameter values incorporated into the model were estimated by laboratory rearing experiments. To validate the present model, the development of eggs laid monthly from June 1 through November 1 was simulated under dynamic temperature and photoperiod conditions at Ayabe City. The individuals laid on June 1 did not enter diapause but emerged in early August of the same year. On the other hand, about 2/3 of the individuals laid on July 1, and all those laid on August 1 and September 1 entered diapause (or quiescence), and started to emerge in late May of the following year. Individuals laid on October 1 and November 1 overwintered as young larvae (1st-3rd stadia) and eggs, respectively, and the majority of these emerged in late July-early August. Interestingly, the remaining individuals entered diapause in the 2nd year and emerged in June of the 3rd year. Analyses of these simulation results suggested that concentrated emergence of P. hilaris can occur twice in one year (in late May-early June and in late July-early August) at Ayabe, and this is fairly concordant with known adult prevalence at this location considering the long life-span of adults. It was also suggested that although P. hilaris at Ayabe has basically a univoltine life cycle with a facultative diapause, varying proportions of the population appear to have a bivoltine life cycle or a semivoltine life cycle depending on the meteorological conditions of that year. The life cycle of P. hilaris is suggested to be very flexible and adaptive to environmental fluctuations.