The biology of spider populations in alder woodland (with an emphasis on the energy dynamics of robertus lividus (Theridiidae) and meta segmentata (Argio Pidae)

A. survey of a spider community in alder woodland was carried out between I967 and I969. From the information on distribution, abundance, and standing states of spiders, two species were selected for an energetics study. Robertus lividus and Meta segmentata, having different ecological characteristics, were used to evaluate the flow of energy (A) through spider populations. The energy assimilated (A) was estimated from the sum of net production (P) and respiration (R Such estimates depend from the outset on reliable data on numbers of individuals, for which purpose appropriate sampling methods were devised. Survivorship and individual growth curves, which were constructed from density and individual biomass at each census, were used to estimate net production, Calorific equivalents were obtained with a miniature bomb calorimeter, A constantly recording device measured specific metabolic rates at given temperatures. By regression analysis, these rates were related to field temperatures. An oxy-calorific value was then used in conjunction with population biomass at each census, to estimate calories expended during maintenance metabolism.