[6] Notable species are the Hawaiian happy face spider (T. grallator), named for the iconic symbol on its abdomen, and T. nigroannulatum, one of few spider species that lives in social groups, attacking prey en masse to overwhelm them as a team.

The epigyne can vary, but the pedipalp has a median apophysis and a colulus is absent from both genders.

It involves pseudocopulation, numerous sperm inductions and copulatory sequences.

Female Theridion are less aggressive after mating compared to other genera of theridiids.

[6] However, the genus has traditionally been assigned species that lack a colulus and did not fit into other genera (wastebasket taxon).