Diversidade e tamanho de himenopteros parasitoides de Brevicoryne brassicae L. e Aphis nerii Boyer de Fonscolombe (Hemiptera: Aphididae)

The objective of this work was to record the diversity of parasitoid of two aphid species, Brevicoryne brassicae L. and Aphis nerii Boyer de Fonscolombe in a site at Uberlandia, MG, and the relationship between parasitoid size and their mummies size, with reference to the host species. B. brassicae were collected on kale (Brassica oleracea L. var. acephala D.C.) and A nerii on milkweed (Asclepias curassavica L.). Samplings were made monthly from May, 1999 to May, 2000 in two experimental gardens. Morphometric measurements for both aphids and parasitoids were simplified by PCA analysis to achieve a multivariate size index. The parasitic Hymenoptera species associated with A. nerii were also found as parasitoids of B. brassicae, but with distinctive relative frequencies. Diaeretiella rapae (M'Intoch) (93.2%), Aphidius colemani Viereck (4.5%) and Lysiphlebus testaceipes (Cresson) (2.3%) were the parasitoids obtained from B. brassicae. Hyperparasitoids associated with these parasitoids were Alloxysta fuscicornis (Ashmead) (57.8%), Syrphophagus aphidivorus (Mayr) (25.1%) and Pachyneuron sp. (17.1%). The parasitoids found in A. nerii were: L. testaceipes (96.1%), A. colemani (3.9%) and the hyperparasitoids Pachyneuron sp. (85.2%) and S. aphidivorus (14.8%). Parasitoid size was correlated with mummy size for both A. nerii and B. brassicae. S. aphidivorus from A. nerii were significantly larger than those from B. brassicae. However, such differences were not detected for L. testaceipes, A. colemani or for Pachyneuron. Mummies of A. nerii were significantly larger than those of B. brassicae. No sexual dimorphism for size was detected.