Studies on the ecology and energetics of Neobisium muscorum (Leach) and Chthonius orthodactylus (Leach) (Pseudoscorpiones: Arachnida).

The population dynamics and phenology of 2 species of predatory soil arthropods, Neobisium muscorum (Leach) and Chthonius orthodactylus (Leach) (Pseudoscorpiones : Arachnida), were studied for a two year period in a beech wood community. A stratified random sampling method was employed, and the sample was divided into leaf litter, humus and topsoil for extraction. 10 samples of 0.1m2 were taken from the sample site every 14 - 28 days over the study period. A modified heat extractor was designed and constructed for use in the study, and the characteristics of the extractor were investigated. Field temperatures at the sample site were measured hourly at nine positions in the soil profile, by a Grant temperature recorder, over the study period. These data were analysed by computer program. In both pseudoscorpion species, maximum densities were recorded during autumn and winter, and minimum densities during spring and summer. 2 generations a year were produced by the Neobisium muscorum population, in spring and autumn. The autumn generation was found to be the most important. The life cycle of Chthonius orthodactylus was found to be univoltine with no free-living protonymphs. Deutonymphs appeared in the population during the autumn months. The horizontal and vertical distribution patterns of both species of pseudoscorpion were investigated. Both populations were shown to aggregate, and the transformation needed to stabilise the variance of the population density estimates was calculated. There was no evidence for either species undergoing a winter hibernation in the humus layer, as had been reported. Respiration studies were carried out on individuals of all life stages of Neobisium muscorum, and the adults of Chthonius orthodactylus, at 5°, 10° and 15°C, using a Cartesian Diver micro-respirometer. The population metabolism of Neobisium muscorum was calculated for two yearly periods using a computer method, from data calculated for the field temperatures, population density and phenology, respiration studies and biomass estimates. Annual production and net population production efficiencies for Neobisium muscorum were calculated for the two yearly periods. The standing crop of both species of pseudoscorpion, over the study period, was estimated by means of bomb calorimetry of all life stages. The importance of pseudoscorpions as part of the predatory fauna of the beech wood community was discussed, and a comparison of the energetics data for Neobisium muscorum was made with published data for other predators.