Video analysis of predation by polyphagous invertebrate
predators in the laboratory and field.
This paper describes field and laboratory time-lapse video analyses of the behavioral responses of the groups: Arachnida: Acari, Araneae, and Opiliones; Myriapoda: Chilopoda; Hymenoptera: Formicidae; Crustacea: Isopoda; and Coleoptera: Staphylinidae to live eggs of the brown blowfly, Calliphora stygia F. (Diptera: Calliphoridae), used as factitious prey in two contrasting agricultural field margins and in the laboratory. Field video results showed that predation by mites was greatest in tree-lined boundaries while centipede numbers and activity were greater in post-and-wire boundaries. All except Staphylinidae showed clear diurnal patterns of activity and egg predation rate over the 12 h recording period. Based on the number of eggs removed, number of eggs examined, predator numbers, and predator activity, three indices were formulated that allowed predator groups to be ranked according to their effectiveness as predators. Commensal interactions between the mites and harvestmen, mediated via mite-pierced eggs, were suggested from field data and confirmed in the laboratory. Phalangium opilio preferred to feed on both manually and mite-pierced compared with untreated eggs, but showed a stronger preference for manually pierced ones than mite-pierced, consuming six times as many over the same period. This is the first demonstration of a commensal interaction between two agroecosystem predators. If commensalism is common in agroecosystems it could increase the effectiveness of biological control. It may also need to be incorporated within theoretical models and may complicate the extrapolation of laboratory-based feeding studies to field situations.
Video; Arachnida; Opiliones; Phalangium opilio; Anystidae; Macrochelidae; Parasitidae; Erythraeidae; Predation; Brown blowfly; Calliphora stygia; Commensalism