Pakistan Journal of Biological Sciences1028-88801812-5735Asian Network for Scientific Information10.3923/pjbs.2003.905.909QayyumAbul 102003610The architecture of the Brussels sprout plant played a role in the host partitioning by the two parasitoid species. D. rapae mostly visited the middle and lower leaves, while A. colemani visited the upper leaves. This indicates that some factor (s) is involved in this type of host sharing. It was observed that D. rapae flew directly to the plant from the vial in a cage, while A. colemani first flew to the top of the cage (towards light) and then landed on the upper leaves of a plant. Attraction to plant chemicals for A. colemani is neither reported in the literature nor was it observed in the present study. These observations may lead to such questions; are A. colemani not responding to the chemicals of the host-plants? Is A. colemani visually attracted to host-plants in bright daylight? Another possible explanation of oviposition by the two parasitoid species at the different strata of the plant is that D. rapae was first attracted to honeydew on the upper surface of the lower leaves and then moved upwards to the lower side of the middle leaves, where they found the aphids, suggesting that females are not responding to honeydew. However, in the presence of other parasitoid species, A. colemani also oviposited more on upper leaves than the other leaves and D. rapea oviposited more on the middle/lower leaves than upper ones. This indicates that these two parasitioid species, when together, partition their hosts partly via plant architecture.]]>Ayal, Y.,1987Diaeretiella rapae: I. The concept of the elementary unit of foraging.]]>5610571068Chow, F.J. and M. Mackauer,198641243254Gardner, S.M., S.A. Ward and A.F.G. Dixon,1984Aphidius rhopalosiphi: A consequence of aphid defensive behaviour.]]>9149155Hofsvang, T.,1988Ephedrus cerasicola.]]>48233239Lawton, J.H.,19861986pp: 265-287pp: 265-287Lewis, W.J., L.E.M. Vet, J.H. Tumlinson, J.C. van Lenteren and D.R. Papaj,19901911831193Qayyum, A.,1999Diaeretiella rapae (McIntosh) and Aphidius colemani (Viereck) sharing the same host species, Myzus persicae (Sulzer).]]>1999Van Alphen, J.J.M. and F. Galis,1983Asobara tabida Nees, a larval parasitoid of Drosophila.]]>52937952Van Alphen, J.J.M. and M.A. Jervis,19961996pp: 1-62pp: 1-62Van Alphen, J.J.M. and L.E.M. Vet,19861986pp: 23-61pp: 23-61Van Dijken, M.J. and J.J.M. Van Alphen,199823265270Van Emden, H.F.,1965Brevicoryne brassicae) on an adjacent crop.]]>2171196Van Steenis, M.J.,1995Aphis gossypii.]]>75151157Van Steenis, M.J. and K.A.M.H. Khawass,1995Aphidius colemani searching for Aphis gossypii: functional response and reaction to previously searched aphid colonies.]]>3339347Vinson, S.B.,19751975pp: 14-48pp: 14-48