Opisthonotal gland

Astigmata and some Oribatida spp. are known to possess a pair of well-developed secretory glands, the opisthonotal glands, located in the opisthosoma... 

Two compounds present in the opisthonotal glands, with each having separate pheromonal functions. 

S. elongata is an example of the second category. At high doses, neral (2) acts as an alarm pheromone (Kuwahara et al, 2001), whereas at lower doses the compound attracts females (Nishimura et al., 2002). Because females of this species can reproduce parthenogenetically, the reason for this function as an attractant is not clear. Possible function may be as an aggregation pheromone. In addition, there are many other mite species in which the major component of the opisthonotal gland secretions functions as the alarm pheromone, and it is entirely possible that these compounds may be found to have additional pheromonal functions at lower doses. 

Howard, R. W., Kuwahara, Y., Suzuki, H. and Suzuki, T. (1988). Pheromone study on acarid mites. XII. Characterization of the hydrocarbons and external gland morphology of the opisthonotal glands of six species of mites (Acari Astigmata). Applied Entomology and Zoology 23 58-66. 

Apart from laterally discharged aggressive compounds from opisthonotal glands, some oribatid mites produce a sticky substance that deters ant attacks.103... 

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