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Keywords:

  • Collembola;
  • computerized vision system;
  • Cox regression;
  • dimethoate;
  • Gamasida;
  • Isotomidae;
  • Laelapidae;
  • predator–prey interactions;
  • predatory behaviour;
  • soil arthropods

Abstract

Short-range predator–prey interactions among small soil-dwelling arthropods are poorly understood. In this study, we measured the behavioural interactions between the predacious mite Hypoaspis aculeifer Canestrini (Gamasida: Laelapidae) and its collembolan prey Folsomia fimetaria L. (Collembola: Isotomidae) and the influence of sex, size, starvation, and poisoning with the organophosphate dimethoate. Pairs of mite and springtail were placed in 18-mm diameter test arenas with a plaster of Paris substrate and their behaviour were measured by a computerized vision system, which automatically detected the locomotory activity of the two animals, their encounters, and the precise time of capture and killing. Data suggest that neither the mite nor the springtail possesses near-field sensory detection of the opponent. A Cox regression model showed that mite sex, size ratio between the predator and prey, average mite velocity, and encounter rate had a significant influence on the mite-capture efficiency (springtail survival). Female H. aculeifer demonstrated higher capture efficiency than males by catching and killing their prey after fewer encounters. Surprisingly, starvation had only a moderate effect on the mite locomotory behaviour and no influence on the capture efficiency as such. Also, springtail survival was independent of its moulting stage. Sublethal poisoning with dimethoate, on the other hand, dramatically increased the mite's capture rate, probably by impeding the evasive response of the springtail.