The potential of Tachyporus spp. (Coleoptera: Staphylinidae) as predators of cereal aphids.

Abstract

The mean numbers of I/II instar Metopolophium dirhodum consumed by Tachyporus obtusus adults increased linearly with temperature from 2.8 per day at 10°C to 8.9 at 25°C. At 20°C the mean numbers of aphids consumed per day by T.hypnorum first-, second- and third-instar larvae were 6.3, 9.6 and 13.2 respectively. The mean total number of aphids eaten throughout larval life was 95.6. The percentage of aphids which were totally consumed by the larvae increased with age, from 8% on the day of hatching to over 97% after the fourth day. Female T.hypnorum ate significantly more aphids per day than males. Type III functional responses were exhibited when T.hypnorum adults were confined with different densities of aphids, either in petri dishes or on plants in the laboratory. At high aphid densities up to 33 I/II instar aphids were consumed in a day by an adult. The capture efficiency of T.hypnorum and T.chrysomelinus adults was highest for I/II instar aphids ( 60%) and lowest for adult alatae (c.35%). Handling times for these two species varied from c.9 min with I/II instar aphids to 20-30 min with adult aphids. T.hypnorum adults and larvae preferred I/II instar aphids to III/IV instars and the adults also preferred apterous to alate adult aphids.