Aspects of the ecological energetics of the wolf spider Pardosa (Lycosa) lugubris (Walckenaer)

Abstract

Feeding experiments were carried out on various stages of the wolf spider Pardosa lugubris in order to construct an energy budget for the spider. Under the rearing conditions the spiders developed at a similar rate to those in the field. P. lugubris females ingest 308 cal during their life. 73.0% of this energy, goes into respiration and 25.7% into production. Males ingest 98 cal of which 81.3% goes into respiration and 16.1% into production. P. lugubris ingests a large proportion of the food it kills and it resembles other arthropod carnivores in having high growth efficiencies. The annual rate of energy flow through a wolf spider population was calculated. 1.39 Kcal/m²/year are “killed” of which 81.2% is ingested. Of this ingested energy 71.1% goes into respiration and 26.4% into production. The difficulties involved in the assessment of the results of single-species energetics studies are discussed. The annual population energy budget of P. lugubris is compared with that of Pyrrhosoma nymphula, an aquatic arthropod carnivore with a similar lifecycle to P. lugubris. Although the magnitudes of the various components of the energy budget are larger in P. nymphula, there are similarities between the two species. Thus, the amount of energy “killed” per unit of predator biomass is similar and a similar proportion of this energy is returned to the ecosystem, although proportionally more goes into decomposers in P. lugubris.