Host Instar Preference of the Aphid Parasite Praon pequodorum (Hymenoptera: Aphidiidae)
Sequeira, Richard; Mackauer, Manfred
Oviposition preference of the hymenopterous parasite Praon pequodorum Viereck 1917 (Hymenoptera: Aphidiidae) for apterous instars of the pea aphid, Acyrthosiphon pisum (Harris 1776) (Homoptera: Aphididae), was evaluated in the laboratory. Mated females laid eggs in all 4 aphid instars. The total number of eggs laid and the total number of aphids parasitized varied among instars when parasites were given a choice between equal numbers of each instar. The preference pattern was evaluated by the fitting of log-linear models to the total number of eggs laid in each of the 4 instars, as determined by host dissection. The calculated probability-ratios indicated a preference for the larger aphid instars: L 1 < (l2 = L4) < l3 when instars were compared pairwise, and L1 < (l2 = L3 = L4) when all 4 instars were provided at the same time. It is suggested that aphid size as well as defensive behaviour influence host instar selection in P. pequodorum. Experimental design and method of evaluation may bias conclusions about parasite preference.