Anti-predator creches and aggregations of ant-mimicking jumping spiders (Araneae: Salticidae)

Myrmarachne assimilis, an ant-like jumping spider (Araneae, Salticidae) from the Philippines and a Batesian mimic of Oecophylla smaragdina, the Asian weaver ant, aggregates on leaves in the company of its model. All stages in this species' lifecycle are sometimes found in nest complexes (nests connected to each other by silk). Although aggregating and forming nest complexes is known for a few other salticid species, the aggregations of M. assimilis have some unusual characteristics. In particular, reproductive females appear to be most frequently found with other reproductive females in nest complexes, suggesting that nest complexes have a role in parental care and are often built by females joining other females. An egg-survival experiment showed that eggs in solitary nests were more often destroyed than were eggs in nest complexes, suggesting that, for females of M. assimilis, choosing aggregations as oviposition sites may be functionally akin to life insurance for their progeny. (C) 2008 The Linnean Society of London.