The effect of choice and no-choice access on host (Aphis fabae) instars preference, in different ages and sizes of Lysiphlebus fabarum (Hymenoptera: Braconidae: Aphidiinae)

The influence of parasitoids on population dynamics is affected by host instar preference. The preference pattern of host instars is not fixed and is modified by the availability and relative abundance of host instars, intensity of defensive behaviors in a particular instar, and also maternal effects of the female forager. In this study, host instar preference of the thelytokous strain of Lysiphlebus fabarum (Marshall) was studied in relation to progeny performance in choice and nochoice experiments, using the first, second, and fourth host instars of Aphis fabae (Hemiptera: Aphididae) as hosts. In addition, we investigated whether the maternal effects (age and size) influenced preferenceperformance associations. Based on the results, offsprings emerging from hosts that were parasitized as the first instar stage were smaller and took longer to develop than offsprings emerging from hosts that were parasitized as the second and fourth instars, irrespective of the age and size of their mothers. The results also showed that when females were offered different host instars under nochoice access, there was no preference for a specific instar, irrespective of the size and age of the female. However, in a choice situation, for the both age and size classes of the parasitoid mother, the number of mummies declined with increasing host instar, suggesting that host instar preference does not reflect offspring performance. For mass rearing of L. fabarum, it would be better if female foragers be introduced to lower density of first instar, under choice situation because of increasing offspring performance.