• cooperation;
  • group foraging;
  • group living;
  • insect size;
  • social spiders


  • 1
    Social species in the spider genus Anelosimus predominate in lowland tropical rainforests, while congeneric subsocial species occur at higher elevations or higher latitudes.
  • 2
    We conducted a comparative study to determine whether differences in total biomass, insect size or both have been responsible for this pattern.
  • 3
    We found that larger average insect size, rather than greater overall biomass per se, is a key characteristic of lowland tropical habitats correlating with greater sociality.
  • 4
    Social species occupied environments with insects several times larger than the spiders, while subsocial species nearing dispersal occupied environments with smaller insects in either high or low overall biomass.
  • 5
    Similarly, in subsocial spider colonies, individuals lived communally at a time when they were younger and therefore smaller than the average insect landing on their webs.
  • 6
    We thus suggest that the availability of large insects may be a critical factor restricting social species to their lowland tropical habitats.