Effect of Aphis gossypii Glover, Brevicoryne brassicae (L.), and Megoura viciae Buckton (Hemiptera: Aphidoidea) on the development of the predator Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae)

Abstract

Laboratory experiments were carried out to evaluate the influence of the aphids Aphis gossypii Glover, Brevicoryne brassicae (L.), and Megoura viciae Buckton on the development of the coccinellid Harmonia axyridis (Pallas). Adult H. axyridis consumed significantly more individuals of the smallest aphid, A. gossypii, than the two larger species, and females consumed twice as many of all three prey species as males. On the other hand, when aphid size (relative weights) was taken into account, it is likely that a greater weight of M. viciae was consumed. H. axyridis did not complete its development when fed exclusively on either B. brassicae or M. viciae, but when fed on A. gossypii, reproduction started about 8 days after emergence from the pupal stage. The 1st-instar larval stage was also shortest when fed on A. gossypii (1.8 days), but took 3.5 days and 4.7 days when fed on M. viciae and B. brassicae, respectively. In addition, larvae fed on A. gossypii were larger and heavier than those fed on the other two aphid species. When larvae were fed exclusively on M. viciae, all but one failed to reach the 3rd instar. However, when fed on A. gossypii during the 1st instar and then on M. viciae in subsequent instars, larval H. axyridis completed their development. It was concluded that M. viciae was either toxic to the 1st-instar larvae of H. axyridis or was an unsuitable host for their development.