Coxal gland

The coxal gland is a gland found in some arthropods, for collecting and excreting urine. They are found in all arachnids (with the exception of some Acari), and in other chelicerates, such as horseshoe crabs. The coxal gland is thought to be homologous with the antennal gland of crustaceans. The gland comprises of an end sac (saccule), a long duct (labyrinth) and a terminal bladder (reservoir). There is generally only one pair (two in some spiders), and they open on the coxae of the walking legs. The coxal secretion of adult female ticks of Ornithodoros erraticus contains a sex pheromone.