Spider sense

Spiders face potential predators on a daily basis, yet, surprisingly, ants are rarely reported as foraging on the webs of orb-weaving spiders. A recent study has found a novel way in which spiders ward off ant invasion.1

The team conducted the study at the National University of Singapore where they tested the silk of orb spiders Nephila antipodiana. They found that a pyrrolidine alkaloid, 2-pyrrolidinone, is present on the silk of the spiders and this was shown to deter three species of ants.

The ontogenetic change in the production of 2-pyrrolidinone suggested that this compound represented a natural adaptive response to the threat of common enemies, rather than a by-product of silk synthesis.

Using GC–MS, the chemical was found to be present only on the silk threads produced by adult and large juvenile spiders; it was absent on threads produced by small juvenile spiders. The team believed that this was due to the thinner silk of juvenile spiders, which the ants were unable to use.

1 Shichang Zhang et al., Proc. R. Soc. B, 2011, DOI: 10.1098/rspb.2011.2193

This story originally appeared in The Column. Click here to view that issue.