[4] The genus Algidia contains the following species and subspecies: Forster's revision includes a key to these taxa.

[4] Forster also incorporated this information in a larger key to New Zealand Opiliones published in two parts.

[5][6] Algidia has a row of prominent tubercles (cone-shaped protuberances) on the forward edge of the carapace.

Molecular studies using Sanger[8] and ultra conserved element[9][10] sequencing showed Algidia is part of a clade that includes the majority of New Zealand triaenonychid genera, as well as several genera from Australia, New Caledonia and South America.

[10] It is most closely related to Prasma and Triregia from New Zealand, and Diaenobunus and Triconobunus from New Caledonia.