Astigmatic mites and many oribatids have a pair of lateral opisthonotal glands often visible as large black, brown, yellow, or red spots. The gland duct orifices are protected by a cuticular flap and the secretions contain a variety of volatile compounds that may serve as alarm pheromones, aggregation and/or sex pheromones, or as defense substances against fungal or predatory attacks. Rarely, as in the oribatid mites of the genus Hermanniella, the gland has a spout-like opening.
Similar glands are found on holothyrans, ticks (the sensilla sagittiformia), and some Opiliones (Sironoidea). Harvestmen also have repugnatorial glands on the prosoma, and many other kinds of arthropods have glands or gland-like structures.
Many arthropods have gland like structures on their abdomens or thoraces (e.g., stink glands), but only some mites (Acariformes, Oribatida, Astigmata) have a pair of opisthosomal glands.
Many arthropods have gland-like structures on their abdomens or thoraces (e.g., stink glands), but only some mites (Acariformes, Oribatida, Astigmata) have a pair of opisthosomal glands.
Author: David E. Walter
Content last updated Sept. 2006, unless indicated otherwise
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