Development assay
Three mated adult females from each of the three colonies were
released into separate leaf-disc cages and fed on the same food as
in their stock cultures. The cages were checked at 12 hourly intervals,
at which time the ladybirds were moved to new cages. The
eggs were checked three times a day to determine the incubation
period and rate of hatching. Newly hatched larvae were isolated
in leaf-disc cages containing excess fourth-instar psyllid nymphs,
third-instar aphid nymphs or E. kuehniella eggs. Larvae were
moved to new cages daily and mortality was recorded. Pupae were
held in isolation until adults emerged, whereupon their fresh mass
was obtained on an analytical balance.
An index of larval performance on the A. pistaciae diet relative to
the M. persicae (as reference diet) was calculated using the equation
of Michaud and Olsen (2004):
½ðDTM=DTAÞ þ ðAWA=AWMÞ=2
where DTM = mean developmental time on the M. persicae
diet, DTA = mean developmental time on the A. pistaciae diet,