Eggsac development rates and phenology of agrobiont linyphiid spiders in relation to temperature

Spider densities are often low after winter in annual crops, and crop management decimates spider populations several times per year. Population recovery rates and phenology depend on reproductive and development rates, which in turn are driven largely by temperature. We aimed to quantify the relationships between eggsac development rates and temperature in order to understand the relative value of different linyphiid species for the biological control of agricultural pests. Female adults of nine linyphiid species were collected from winter wheat in the UK over 3 years; Bathyphantes gracilis (Blackwall), Erigone atra (Blackwall), Erigone dentipalpis (Wider), Erigone promiscua O.P.‐Cambridge), Tenuiphantes tenuis (Blackwall) formerly Lepthyphantes tenuis (Blackwall)], Meioneta rurestris (C.L. Koch), Oedothorax apicatus (Blackwall), Oedothorax fuscus (Blackwall), and Oedothorax retusus (Westring). These are agrobiont species that are dominant in agroecosystems. We tested how well development in the field can be predicted on the basis of laboratory experiments. We also built a simple phenology simulation model to test whether spider phenology in the field can be predicted by a general knowledge of the relationship between temperature and development rate. The relationships between temperature and development rates of eggsacs were not linear as described by a day‐degree model, but exponential as described by a biophysical model. Duration of the eggsac development period in the field was predicted accurately from laboratory experiments. We only found minor differences between development thresholds of eggsacs at constant temperatures compared with fluctuating temperatures. The phenology model predicted the phenology of L. tenuis and E. atra well, but the number of generations predicted for O. fuscus was not realised in the field. This suggests that development of this species may be affected by factors other than temperature. The methods used here could also be applied to other natural enemies, to determine whether their thermal biology is conducive to a role as biocontrol agents in disturbed agricultural systems.