Defences of Arachnids: diversified arsenal used against range of enemies.

Arachnida represent a hyperdiverse group of terrestrial arthropods. Although arachnids are mostly predators, they often fall prey to other predators. Here, the diversity of enemies and the defences of arachnids which are used against their predators is reviewed. The main predators of arachnids are other arachnids, followed by insects, mammals and birds. Almost all types of defences has evolved in this class, but countershading, and elusiveness await to be discovered in Arachnida. Overall, empirical evidence is rare but has slowly been accumulating over the last decade. Anachoresis is used most frequently across all orders
only in Acari, Araneae, Opiliones, and Solifugae it is rivalled by background matching, and Batesian mimicry. The number of different types of defences used by an order is positively correlated with the number of predatory groups preying on it. The major gaps are identified and future avenues for investigation – cases which deserve special attention because these may reveal completely new phenomena – are proposed. It is concluded that this group offers a very diverse array of defences which has not been sufficiently studied
thus, this review aims to stimulate further research.