Librodor japonicus (Coleoptera: Nitidulidae): Life history, effect of temperature on development, and seasonal abundance

Librodor japonicus (Motschulsky) is distributed throughout the satoyama forests in Japan, and inhabits the saps of oak trees all its life. Although the beetle is a potential indicator of bio-resource abundance in the satoyama forests, the life history traits and seasonal abundance have not been studied. In this study, first, the seasonal abundance of L. japonicus was investigated using banana bait traps in Okayama City in 2002. Two peaks of abundance were found: a large peak from April to June and a small peak from August to September. The beetles oviposited on banana slices, and a successful artificial rearing method was established using only banana slices and leaf mold. The effect of temperature on the survival rate, adult size and developmental period was examined at different temperatures. The survival rate and the adult size tended to be greater at 25°C than at other temperatures. The thermal thresholds and thermal constants calculated from egg to adult development were 5.6 and 5.9°C and 1,010.9 and 1,022.0 degree-days for females and males, respectively. On the basis of these developmental parameters and the seasonal abundance of L. japonicus, the number of generations per year in Okayama, Japan, was estimated to be one.