Living with the enemy: Jumping spiders that mimic weaver ants

Ants prey on salticids, and encounters with weaver ants (Oecophylla smaragdina (Fabricius 1775)) appear to be especially dangerous for many salticids. In the Philippines, Myrmarachne assimilis Banks 1930 is a salticid that mimics Oecophylla smaragdina. We tested for the abilities of four categories of salticids, plus M. assimilis, to survive in the proximity of weaver ants. The four categories were: (1) myrmecomorphic (ant-like species other than M. assimilis); (2) myrmecophagic (ant-eating species); (3) myrmecophilic (a species that is either myrmecophagic nor myrmecophagic, but is known to associate with ants) and (4) ordinary (species that are neither ant-like nor ant-eating, and are not known to associate with ants). The hypothesis investigated here is that M. assimilis has, compared with other salticids, especially pronounced ability to survive in close proximity with this particular ant species. The individual salticids used in our experiments had not had previous contact with weaver ants or any other ants. When confined with groups of 10 weaver ants, the myrmecomorphic, myrmecophagic and myrmecophilic species survived significantly more often than ordinary salticids, but Myrmarachne assimilis survived significantly more often than all other categories. When kept with groups of 20 ants, there was a proportional decrease in the number of salticids that survived within each salticid category. However, few salticids survived when confined with groups of 40 ants, regardless of category.