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Pseudoscorpions are predators of arthropods and primarily inhabit soil litter and tree bark in forests, although some species have been collected from animal nests, suggesting close associations with mammals and birds. We made preliminary observations on the life cycle and life history traits of Megachernes ryugadensisMorikawa, 1954, phoretic on the wood mice Apodemus speciosus and A. argenteus, by sampling wild specimens in the field and rearing these specimens in a laboratory. The main phoretic host at the study site was A. speciosus; we observed an average of 1–1.7 pseudoscorpions on 5–36% of mice within the 2-year study period. The observed phoretic stages of M. ryugadensis were adults and tritonymphs; the phoretic ratio on A. speciosus was relatively stable for 2 years. The duration of full development from egg to adult in M. ryugadensis was unclear, probably due to unsuitable rearing conditions; however, individuals survived as adults for over one year. Typical maternal care was confirmed in pseudoscorpions and egg hatching was synchronized to within ca. 8 h. Further study, including close examination of mouse nests, is required to elucidate the symbiotic relationship between the pseudoscorpion and host rodents.

Ovary contents and insemination status were examined in overwintered queens of Vespa mandarinia that were collected using bait traps in Ibaraki Prefecture, eastern Japan. Catches in the traps occurred from late April to early July in 1999, though they were few or rather sporadic in and after June. Fertilization rates were 100% in 1999, and 93% in 1998 when a preliminary sampling was made. While the ovary index (number of eggs with size equal to or larger than adjacent nurse cells) of queens caught on the first few collection dates was small, it rapidly increased up to late May. Generalized linear model analyses showed that the ovary index depended both on collection date and the size (head width) of the queens. Mature eggs were almost absent in their ovaries before early May, whereas more than 70% of the queens had one or more mature eggs on and after May 10, suggesting the onset of nesting in early May.