Theridion

The spider genus Theridion, after which the family Theridiidae is named, consists of almost 600 described species that occur all around the world. Notable species are the Hawaiian happy face spider – T. grallator – and T. nigroannulatum, which is one of the very few species of spiders which live in social groups and not merely aggregate by coincidence. They live in large colonies, lying in wait for passing prey purportedly concealed under the edge of a leaf or stick with threads trailing down beneath them. If an insect intrudes, interjecting itself into the web, the spiders respond en masse, overwhelming it as a team. They even take turns helping pull large victims back to their lair. Theridion braueri Simon, 1898 probably belongs into a different genus; however, Robertia the new name proposed by Saaristo (2006) is preoccupied by the mammal-like reptile Robertia.