Cold hardiness in invertebrate poikilotherms

1. 1. A selective review is made of the information on cold hardiness in the following taxonomic groups: Protozoa, Platyhelminthes, Rhynchocoela, Rotifera, Nematoda, Mollusca, Annelida, Tardigrada, micro-Arthropoda (Collembola & Acari) and Arthropoda. 2. 2. Most existing data are for the arthropods and, in particular, the Insecta, within which research has been concentrated on the Lepidoptera, Diptera and Coleoptera. 3. 3. The occurrence of the freezing susceptible and freezing tolerance starategies of cold hardiness within the invertebrates cannot be explained on phylogenetic grounds at present. Considering insects to order level, nine invertebrate taxa are freezing susceptible, five are freezing tolerant, whilst eight groups have both types. 4. 4. Factors from individual species' ecology and morphology may have largely determined the type of strategy adopted.