UC Riverside

Chaetodactylidae mites are kleptoparasites of solitary bees in the families Megachilidae and Apidea. Chaetodactylus krombeini is a North American pest most often associated with Osmia lignaria. Chaetodactylidae mites can cause up to 50% losses of bee offspring in nests and cause adult bees to develop into less efficient pollinators. Managed Osmia beekeepers need control methods for these parasites, however there is little known about C. krombeini life history making it difficult to efficiently decrease their harmful effects. Mite host preference is unclear as there are contradictory reports of male and female bees being the preferred host of the phoretic deutonymph. Host sex preference was examined by recording mite distribution within host nests. Mite distribution determined if phoretic deutonymphs dropped off hosts in female cells (back of nest) or male cells (middle and near nest entrance) during nest building. This experiment yielded low mite numbers within each nest, though mites were found in the back of nests regardless of host sex, possibly indicating mites have a positional preference rather than a host sex preference. Heteromorphic deutonymphs of C. krombeini are hypothesized to be exclusively female. This hypothesis leads to additional hypotheses of C. krombeini requiring arrhenotokous parthenogenesis and oedipal mating to found mite populations. Sex determination assays of the heteromorphic deutonymphs were conducted in 2-week periods for each mite. Inert and phoretic deutonymphs were individually placed in microcentrifuge tubes with a pollen provision then sexed when mites developed into adults. Phoretic deutonymphs were allowed to overwinter with and without a bee host. Males and females developed from both morphs of the heteromorphic deutonymph. Male and female dispersal prior to mating may indicate sexual reproduction is required for this species. Scanning electron microscopy was used to examine C. krombeini morphology to gain insight into life history traits. Specimens of C. krombeini were prepared with ethanol and hexamethyldisilazane. Images will be useful to compare the morphology of C. krombeini to mites with known life history traits and to other species that are indistinguishable from C. krombeini. These experiments contribute to the knowledge of C. krombeini, helping future control efforts of this pest.