TRANSFERS OF VARROA MITES FROM NEWLY EMERGED BEES - PREFERENCES FOR AGE-SPECIFIC AND FUNCTION-SPECIFIC ADULT BEES (HYMENOPTERA, APIDAE)

Movements of the parasitic honey bee mite, Varroa jacobsoni (Oud.) wer e monitored in several assays as they moved among adult host honey bee s, Apis mellifera. We examined the propensity of mites to leave their hosts and to move onto new bee hosts. We also examined their preferenc e for bees of different age and hive function. Mites were standardized by selecting mites from newly emerged worker bees (NEWs). In closed j ars, 50% of Varroa left NEWs irreversibly when no physical path was pr esent for the mites to return to the NEWs; about 90% of mites left new ly emerged drones in identical assays. In petri dish arenas, mites wer e rarely seen off NEW hosts when monitored at 15-min intervals for 4 h ; this was the case for single NEWs with one mite (NEWs+) and when a N EW+ and a NEW- (no mites) were placed together in a petri dish. When a NEW+ was held with either a nurse bee or a pollen forager, 25% of the mites moved to the older bees. When both a nurse and a pollen forager were placed in a petri dish with a NEW+, about 50% of the mites trans ferred to older bees; nurse bees received about 80% of these mites, wh ereas pollen foragers received significantly fewer mites (about 20%, P < 0.05). Most mite transfers occurred during the first 30 min after c ombining NEWs+ and test bees. When NEWs+ were combined with bees of kn own ages, rather than function, mites transferred more often to young bees than to older bees (1- and 5-day-old bees vs. 25-day-old bees, P < 0.05; 1-day-old vs. 13- and 25-day-old bees; P < 0.05). No differenc es in proportions of transferring mites were seen when the range of be e ages was less than or equal to 8 days (P > 0.05), implying that the factors mediating the mites' adult-host preference change gradually wi th bee age. A possible chemical basis for host choice by Varroa is ind icated by their greater propensity to move onto freezer-killed nurse b ees than onto freezer-killed pollen foragers (P < 0.05) and by their l ower movement onto heat-treated bees than onto control bees (P < 0.05) . Bee age, hive function, and directional changes in cuticular chemist ry are all correlated. Movements of newly emerged mites in relation to these variables may provide insights into their reproductive success in Apis mellifera colonies.