Specialized exploitation of ants (Hymenoptera: Formicidae) by spiders (Araneae)

Jackson, R.R.; Nelson, X.J.

Abstract: Ants are a dominant resource in the spider's world, and spiders have a variety of ways of exploiting this resource. Two broad domains of exploitation are reviewed, namely specializing on ants for food and specializing on ants for models to mimic. Exploiting of ants as a source of food includes preying on worker ants and also taking food out of the ant's mandibles. Experiments have revealed numerous examples of spiders that specialize on ants by deploying ant-specific prey-capture behaviour. Consistent with other evidence that predatory versatility is widespread among spiders, many of the spiders that specialize at preying on ants sometimes adopt alternative tactics for capturing ants and are also proficient at targeting other prey. The venom, enzymes and sensory systems of spiders can also be specialized for preying on ants. Many spiders adopt Batesian mimicry of ants for protection against predators that readily eat spiders but have an aversion to ants. For these spiders, one of the costs of mimicking ants is attracting the unwanted attentions of spiders that specialize at preying on ants. Sometimes spiders solve this problem by making use of a conditional anti-predator strategy of resembling ants by default but switching to behaviour unlike an ant when ant-eating predators are encountered. Batesian mimicry of ants is sometimes communal (i.e., ant mimics living in groups appear more formidable because of the group's resemblance to a group of ants) and communal Batesian mimicry can then be deployed as a part of an aggressive-mimicry strategy. Ant-averse spiders may abandon their broods when confronted by a swarm of ants and likewise they flee when confronted by a swarm of communal ant-mimics, with the mimics then feeding on the unguarded broods. Other spiders use Wasmannian mimicry based on acquiring the cuticular hydrocarbons of ants as a means of safely mingling with the ants and then robbing the ants of their broods.

Myrmecol. News 17: 33-49; printable