Huddling and the control of water loss by the slug Limax pseudoflavus Evans

Limax pseudoflavus Evans form closely packed huddles within their day-time resting sites. Huddles will form in two populations of this species are mixed. Huddles will also form if L. pseudoflavus and L. flavus are mixed, but individuals tend to select conspecific neighbours within the huddles. Huddles form only after considerable milling around of the component slugs and form more frequently and involve more contact in dry compared with humid conditions. Moving slugs increase their evaporation rate by 65% compared with still animals of the same weight. Two slugs making close contact reduce their evaporation rate by 34% compared with unhuddled slugs. It is argued that huddles are non-social aggregations whose prime function is the conservation of water.