The odoriferous glands of some Palpatores Phalangida (Opiliones) (Arachnida)
Holmberg, Robert G.
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The odoriferous glands of especially Phalangium opilio and to a lesser extent Opiliones parietinus, Odiellus pictus, Homolophus biceps, Leiobunum calcar and L.. vittatum were investigated by: external examination; dissection; light microscopy; predator-phalangid encounter experiments with amphibians, birds, mammals, spiders, centipedes and ants. Amphibian stomach content analysis and a field experiment involving frogs as predators were also performed. No liquid odoriferous gland secretion was observed externally in P. opilio, O. parietinus or O. pictus. Liquid secretion may have been present in H. biceps. Only P. opilio and H. biceps produced a detectable odor. Observations on the construction of the glands confirmed previous, descriptions. However, it was shown that the phalangids studied have some control over which gland operates and that the secretions probably differ between species. Vertebrate-phalangid encounter experiments suggest that all vertebrate predators can eat phalangids of the suborder Palpatores without harm. Although a number of spiders and one species of centipede were not repelled by the odoriferous glands, some spiders and an ant species were repelled. It is concluded that phalangid odoriferous glands are most likely defensive in function, although limited in effectiveness, and are not used for trail marking, species recognition, sexual recognition, anti-microbial protection or excretion.