We examined the effects of selection cutting on the longicorn and scolytid beetle assemblages in an old-growth mixed conifer-broadleaf forest in Hokkaido. We collected these beetles in the selection cutting and non-cutting sites in the old-growth forest using collision traps baited with chemical attractants. In longicorn beetles, species richness, abundance, diversity indices, species composition and the number of individuals of each species did not differ significantly between the selection cutting and non-cutting sites before selection cutting. However, two years after selection cutting, species richness and the number of individuals of three species of Lepturinae were significantly greater in the selection cutting site than in the non-cutting site. This would be resulted from increased relative light intensity and canopy openness after selection cutting. These factors could enhance the attractiveness of the traps to flower-visiting species. In scolytid beetles, no significant effects of selection cutting on species richness, abundance, diversity indices, species composition and the number of individuals of each species were detected. Previous studies have reported negative effects of selection cutting on forest insects, particularly on saproxylic species. However, this study did not detect such effects probably because (1) the amount of dead wood did not decrease with selection cutting, (2) the study areas were too small, and/or (3) the old-growth forest was too small and was isolated from other old-growth forests.

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Biology of Elenchus japonicus (Esaki et Hashimoto) was studied by rearing host delphacid planthoppers, Sogatella furcifera (Horvath) in 2 types of vials (Diameter: 20mm; Length: 10 and 18cm) in 1985. The 1st instar larvae of E. japonicus mostly preferred the 2nd to 5th instar larvae of S. furcifera as hosts. The duration of emergence of the 1st instar larvae from the maternal body continued for 12 hours, and these larvae survived up to 15hrs. The 1st instar larvae gnawed with their mandibles the inter-segments between either ventral or dorsal terga to invade the host's body, but position of the inter-segments used was not fixed. The development of immatures in host bodies differed slightly, depending on the host stages into which the 1st instar larvae invaded. The larval development reared at 28℃ was the fastest in the 5th instar larvae of hosts, spending 10 days from invasion of the 1st instar larva to extrusion of the last larva in female stylopids, and for 13 days from invasion of the 1st instar larva to emergence of adults in male stylopids. Both sexes of most stylopids extruded their cephalothoraces at definite positions between the 7th and 8th terga of either side of the pleural membrane of adult hosts, irrespective of their sexes, when they had parasitized singly. However, other stylopids, except for the individual which extruded at a definite position, could extrude at aberrant positions, when they superparasitized. The number of stylopids parasitized/host averaged 1.2 and up to 4 maximum. Sex ratio was slightly male-biased (0.62, 179/288). The mean value of the egg complement of female stylopids that parasitized singly female hosts was 1,237±194 (N=19). However, the values were variable, depending on the host species, sex of hosts, number of stylopids per host, and host generation, reflecting that the size of female stylopids was presumably affected by these factors.

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