短 報(Short communication) Social wasps collected with Malaise traps in Japanese cedar (Cryptomeria japonica) plantations (Hymenoptera, Vespidae)

Social wasps, which are important agents of ecosystem services (as predators) and disservices (as stinging pests), were collected with Malaise traps in Japanese cedar (Cryptomeria japonica) plantations in three regions of Japan (Tohoku, Shikoku, and Kyushu). Each region had 12 study stands that were categorized into the following four types based on the type of management: 1) unthinned, old-age stands (78–102 y; OA); 2) unthinned stands (41–51 y; UT); 3) stands thinned 2–4 y before the study (36–50 y) with felled logs left on forest floors (TL) and 4) stands similar to 3, but felled logs were removed (TR). A total of 350 individuals of 13 species (nine of Vespinae and four of Polistinae) were collected in the three regions. For Vespinae, Vespa simillima and Vespula shidai predominated in every region, making up 38-55% and 32-52% of all vespine wasps collected, respectively. Generalized linear model (GLM) analyses, in which the type of management was used as the fixed factor and regions as the blocking factor, showed that the type of management did not affect the number of species but did affect abundance of V. simillima and Vl. shidai: OA, UT and TR had larger catches over TL in the former, and OA and UT had larger catches over TL and TR in the latter. We discussed the possible reasons why these wasps did not respond positively to thinning, which was different from the results reported for other groups of insects.