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. Spiders are the most common ant mimics. Additionally, some arthropods mimic ants to escape predation (protective mimicry), while others mimic ants anatomically and behaviourally to hunt ants in aggressive 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. Spiders are the most common ant mimics. Additionally, some arthropods mimic ants to escape predation (protective mimicry), while others mimic ants anatomically and behaviourally to hunt ants in aggressive mimicry. In Wasmannian mimicry, mimic and model live commensally together; in the case of ants, the model is an inquiline in the ants' nest. Wasmannian mimics may also be Batesian or aggressive mimics. To overcome ants' powerful defences, mimics may imitate ants chemically with ant-like pheromones, visually (as in Batesian mimicry), or by imitating an ant's surface 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 spider species mimic the social behaviours, morphological features and predatory behaviour of ants. Fourteen genera of jumping spiders (Salticidae) mimic ants. The jumping spider genus Myrmarachne are Batesian mimics which resemble the morphological and behavioural properties of ants to near perfection. These spiders mimic the behavioural features of ants such as adapting their zig-zag locomotion pattern, and the act of creating an antennal illusion by waving their first or second pair of legs in the air. The slender bodies of these spiders make them more agile, allowing them to easily escape from predators. Studies on this genus have revealed the major selection force, the avoidance of ants by predators such as spider wasps, that has driven the evolution of ant mimicry in spiders. Ant mimicry has a cost: the body of spider myrmecomorphs is much narrower than non-mimics, reducing the number of eggs per eggsac, compared to non-mimetic spiders of similar size. They seem to compensate by laying more eggsacs over their lifetimes. 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. Among several Hemiptera (true bugs) that resemble ants are Mirid bugs, the wingless Myrmecoris gracilis which feeds on aphids, while Systellonotus triguttatus, in which nymphs and females strongly resemble ants, is often found in the vicinity of ants. Males of Formiscurra indicus (Caliscelidae) are antlike, but not the females. The phasmid Extatosoma tiaratum, while resembling dried thorny leaves as an adult, hatches from the egg as a replica of a Leptomyrmex ant, with a red head and black body. The long end is curled to make the body shape appear ant-like, and the movement is erratic, while the adults move differently, if at all. In some species the eggs resemble plant seeds, complete with a mimic elaiosome (called a 'capitulum') as in plants that are associated with ants in myrmecochory. These eggs are collected by the ants and taken to their nests. The capitulum is removed and eaten and the eggs continue to be viable. Franklinothrips is a predatory genus of thrips. Especially the females mimic ants in appearance and behavior. Ant mimicry also occurs in other genera of Aeolothripidae, where it has arisen independently, for example Aeolothrips albicinctus in Europe and A. bicolor in North America, the Australian species Desmothrips reedi, Allelothrips with seven species from Africa and India, Stomatothrips with eight species from the Americas. This kind of mimicry probably evolved as a response to the presence of ants.