Prey preferences of six species of Carabidae (Coleoptera) and one Lycosidae (Araneae) commonly found in UK arable crop fields

Laboratory experiments were used to determine the feeding preferences of si x carabid beetles and one lycosid spider on aphid and collembolan prey. The first investigation used only five species of carabid Pterostichus melanar ius Illiger, Pterostichus madidus F., Harpalus rufipes DeGeer, Nebria brevi collis F. and Carabus violaceus L., which had been caught most commonly in pitfall traps in the headland region of arable crop fields. When offered Br evicoryne brassicae L., Sitobion avenae F., Metopolophium dirhodum Walker a nd Rhopalosiphum? padi L. as prey items, the species consistently consumed in high numbers was M. dirhodum. In subsequent experiments four carabids Pt erostichus cupreus L., P. pitfall trapping to extend throughout the arable crop, were the chosen predators. These predators were offered a choice betw een M. dirhodum and entomobryid collembolans (a recognised alternative prey item) to gauge their preference between the two prey types. Both male and female P. cupreus and P. melanarius showed a significant preference for the aphid prey, while there was no significant preference displayed by the oth er species. The effect of temperature on the voracity of these five predato rs fed on M. dirhodum was investigated. There were significant differences in the number of aphids consumed by the species and sexes at the different temperatures. Regression analysis on the mean numbers of aphids eaten by ea ch sex of the five predators, showed that in the majority of cases there wa s a significant increase in predation with increasing temperature. In consi dering the dietary preferences illustrated by these experiments, it appeare d that P. cupreus and P. melanarius offered the greatest potential in contr olling aphids on arable crops.