Summary details for Orchestina sp.

Distribution

The species is known from only one site in North Essex, where it was collected between 1992 and 1994 (Ruffell & Kovoor 1994). It does not appear to have been recorded in Europe.

Habitat and ecology

The spider has been collected on an old ivy-covered wall, from the litter that collects in the close mass of clinging stems and branches. Specimens kept alive in captivity were fed psocids. They made insubstantial retreats, sometimes within a curled leaf and sometimes on the side of the box. Females have been found in March, July, September and November.

Status

Extremely rare. Searches at the one known site produced single females on six occasions, the last in 1994. Significantly, the quality of the habitat declined at this time when the ivy habitat was cut. The absence of further records in over ten years suggests the population size reduction may be approaching 100%. Other potential sites with similar habitat have been searched, so far without success. Oonopids usually have 6 eyes, and lack the anterior median eyes (AMEs) present in most spiders. The first specimen collected in 1992 had 8 eyes, but subsequently some of the individuals found had 6 eyes and some 8 eyes. All had the general appearance and typical reddish-purple markings of the oonopid genus Orchestina. However, femora IV of the Essex specimens are much less swollen than those of typical Orchestina species. Dalmas (1916) in his revision of Orchestina also refers to the sporadic occurrence of AMEs in some species, although the 8-eyed patterns figured are different from that of the Essex specimens. In spite of further intensive searching no males have yet been collected, and it is still unclear whether the Essex specimens belong to Orchestina or to a closely related (new?) genus (Merrett & Murphy 2000).

Threats

The ivy was cut after 1994, and it is not known whether the habitat has been completely destroyed, or will recover.

Management and conservation

Old ivy-covered walls are much rarer than in the past, and wherever possible suitable habitat should be retained. If the spider should be rediscovered then it would be essential to conserve the habitat. Text based on Dawson, I.K., Harvey, P.R., Merrett, P. & Russell-Smith, A.R. (in prep.).