Conformation of the ambulacrum of Varroa Jacobsoni oudemans (Mesostigmata: Varroidae): A grasping structure

Abstract

Contrary to common belief, the authors suggest that the ambulacrum of the adult females Varroa, Euvarroa and probably of Tropilaelaps is not a sucker or a sticky pad but a structure with protractile claw-like sclerites as shown by SEM analysis. These claw-like sclerites may work as crochets to grasp the hairs of the bee and allow the mites to move rapidly on the adult bees and other substrata. The conformation of the ambulacrum may explain why mites are not able to move in dusty or wet surfaces, as noted by Sadov et al. (1980). The humidity and the solid particles may interfere with the grasping abilities of the mites. Immature stages of Varroa and Euvarroa do not seem to have ambulacral claw-like projections as those found in the adults. This is probably due to the fact that the young forms walk on smooth surfaces, as on the bee larvae and the interior of the cell. The morphology, function and origin of the ambulacrum of Varroidae, Tropilaelaps and other phoretic mites are discussed.