The Growth and Voracity of Larvae of Leis Conformis (Boisd.) (Coleoptera: Coccinellidae) Fed on the Rose Aphid Macrosiphum Rosae (L.) (Homoptera: Aphididae) in the Laboratory.

Abstract

The ladybird Leis conformis is one of the commonest predators of the rose aphid, and of other aphids in South Australia. When fed a surfeit of M. rosae the mean weights of larvae during development could be described by the equation: y = 0.45 exp[(O.0313t-0.2751)x] where t is temperature in degrees Celsius such that 15 < t < 29.2, and x is time in days, such that y < 40.6 mg. The mean weights could also be described by: y = exp (0.0347x-0.8551), with x in day-degrees above 10ºC. The voracity of larvae could be described in third-instar aphid equivalents (TIES) by: y = exp(0.0347x+ 0.6219) where y is cumulative number of TIES eaten, and x is less than 131.4 day-degrees. The TIE units used to convert predator wet weight to aphid units eaten were based on the numbers of aphids of each instar that had to be eaten for a predator larva to gain one milligram of wet weight. It is suggested that the voracities of different ladybirds feeding on different aphids can be compared when voracity is expressed as the cumulative number of aphids eaten per stadium. The quantification of voracity in the field, and the possible use of L. conformis for pest control, are briefly discussed.