English Article. The ectoparasitic mite Varroa jacobsoni reproduces in the capped brood of the honey bees Apis cerana and Apis mellifera, Observations on the reproductive behavior of the mite have shown a well-structured spatial allocation of its activity using the bee or cell wall for different behaviors, The resulting advantages for the parasite of this subdivision of the concealed brood environment suggests an important role for chemostimuli in these substrate. Extracts of the European honey bee cocoons induce a strong arrestment response in the mite, as indicated by prolonged periods of walking on the extracts applied on a semipermeable membrane and by systematically returning to the stimulus after encountering the treatment borders, Two thin-layer chromatography fractions of the cocoon extract eliciting arrestment were found to contain saturated C-17 to C-22 primary aliphatic alcohols and C-19 to C-22 aldehydes. We analyzed extracts of the cocoon and different larvae, pupae, and adults of both worker and drone A, mellifera to determine the relative amounts of these chemostimuli in the different substrates employed by Varroa, Both aldehydes and alcohols were more abundant in the cocoon than in the cuticle of adult or developing bees. Mixtures of the aliphatic alcohols and aldehydes at the proportions found in the cocoons acted synergistically on the arrestment response, but this activity disappeared when mixed in equal amounts, When these oxygenated chemostimuli were mixed with C-19 to C-25 alkanes at the proportions found in the cocoon extract, we observed a significantly lower threshold for the chemostimulant mixture, These results indicate how Varroa may use mixtures of rarer products to differentiate between substrates and host stages during its developmental cycle within honey bee brood cells. (C) 1998 Wiley Liss, Inc.