Distribution of Chaetodactylus krombeini (Acari: Chaetodactylidae) in nests of Osmia cornifrons (Hymenoptera: Megachilidae)

Chaetodactylus krombeini (Acari: Chaetodactylidae) is a cleptoparasitic mite of Osmia cornifrons (Hymenoptera: Megachilidae), the Japanese hornfaced bee. Chaetodactylus krombeini negatively impacts the survivorship of O. cornifrons through consuming the developing larvae’s pollen provision or through directly attacking larvae. The consumption of the pollen provision can cause reduced body size in O. cornifrons, and direct attacks may result in mortality. The objective of this study was to determine whether male or female O. cornifrons were more greatly impacted by C. krombeini. Mite distributions based on presence/absence and categorical density values were analyzed for 89 additional nests and regression analysis was used to determine mite distribution within the nests. Cocoons from 20 infested O. cornifrons cells were examined to determine if mites could be found inside cocoons. Trends in O. cornifrons gender distribution showed that female bees were located in the rear of the nest and that males were located in the center of the nest. Regression analysis of C. krombeini showed a preference for the inner cells of the nest. No mites were found inside O. cornifrons cocoons. These trends indicate that C. krombeini may have a greater effect on mortality in the egg and larval stages of female O. cornifrons than in male O. cornifrons.