The temperature preference, phenology and enzymatic activity of two winter‐active spiders (Araneae)

Abstract While the great majority of arthropod natural enemies present in commercial orchards are inactive during winter, a few spider species remain active and catch pests. This is the case of Anyphaena accentuata and Philodromus spp. spiders, which contribute significantly to a reduction in the population of psyllids during winter. These spiders were found to catch prey even at temperatures close to or below 0°C. Here, we investigated whether these spiders have a preference for low temperatures, when they reach maturity, and whether their enzymatic activity, specifically that of α‐amylase, is adapted to low temperatures. The temperature preference, studied on a temperature gradient funnel, showed that Anyphaena preferred temperatures of around 20°C, while Philodromus preferred temperatures of around 30°C. On the basis of faunistic data, both Anyphaena and Philodromus are univoltine, with adults of Anyphaena occurring in late April, while those of Philodromus occur in early June. The amylolytic activity was measured in venom gland extracts and whole prosoma homogenates in the range from 0 to 60°C. Fitted triangular models revealed that α‐amylase in the prosoma of Anyphaena has lower thermostability at higher temperatures than α‐amylase in Philodromus . Fitted Arrhenius models revealed that, in Philodromus , the activation energy of the enzyme reaction in prosoma homogenates was lower than that in venom gland extracts. The obtained results show that Anyphaena is more adapted to lower temperatures than Philodromus .