Ant mimicry

Ant mimicry or myrmecomorphy is mimicry of ants by other organisms. Ants are abundant all over the world, and potential predators that rely on vision to identify their prey such as birds and wasps normally avoid them, because they are either unpalatable or aggressive. Some arthropods mimic ants to escape predation (protective mimicry), while others mimic ants anatomically and behaviourally to hunt ants (aggressive mimicry).

To overcome ants' powerful defences, mimics may imitate ants chemically (Wasmannian mimicry) with ant-like pheromones, visually (as in Batesian mimicry, though the purpose may also be aggressive mimicry), or by copying microstructure for tactile mimicry.

Batesian mimics are species which typically lack strong defences of their own, and make use of their resemblance to well-defended ants to avoid being attacked by their predators, some of which may be ants. There are ant-mimicking arthropods in several different groups, described below.

Young instars of some Orthoptera, such as the katydid Macroxiphus sumatranus, have an "uncanny resemblance" to ants, extending to their black coloration, remarkably perfect antlike shape, and convincingly antlike behaviour. Their long antennae are camouflaged to appear short, being black only at the base, and they are vibrated like ant antennae. Larger instars suddenly change into typical-looking katydids, and are entirely nocturnal, while the adult has bright warning coloration.

Over 300 species of spider in different families are Batesian mimics of ants, such as Sphecotypus in the Clubionidae. In the Salticidae family, ant-mimicking spiders can be discerned from the ants around them by the movements they make to keep the ants at an acceptable distance. Ant hunters often do not resemble ants as much. Even within a closely related group, ant mimicry may have originated several times, as in the Salticidae subfamily Ballinae. Mimicry has a cost: the body of spider myrmecomorphs is much narrower than non-mimics, which reduces the number of eggs per eggsac, compared to non-mimetic spiders of similar size. They seem to compensate by laying more eggsacs in their lifetime. A study of three species of (predatory) mantises suggested that they innately avoided ants as prey, and that this aversion extends to ant-mimicking Salticidae.

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