Biocontrol News and Information
CABI Publishing

December 1996, Volume 17 No. 6

The following papers, of biological control interest, will appear in the Bulletin of Entomological Research in the near future.

Biosystematics of the Cotesia flavipes species complex (Hymenoptera: Braconidae): morphometrics of selected allopatric populations. S.W. KIMANI-NJOGU, W.A. OVERHOLT, J. WOOLLEY and A.K. WALKER, International Centre for Insect Physiology and Ecology, Nairobi, Kenya.

Abstract - Morphometric studies of allopatric populations of the Cotesia flavipes species complex representing three putative species: C. flavipes, C. sesamiae and C. chilonis, were conducted. Sixteen characters were measured. Principal component analysis separated the complex into three somewhat overlapping groups that corresponded well with previous concepts of the species. Canonical variate analysis separated the complex into three distinct clusters, with populations from Africa together, populations from Asia and the Neotropics forming a second cluster, and material from China and Japan forming a third cluster. The Mahalanobis squared distances between the three clusters were nearly equal. Results support recognition of three species in the C. flavipes complex.

Smicronyx species (Coleoptera: Curculionidae), economically important seed predators of witchweeds (Striga spp.) (Scrophulariaceae) in sub-Saharan Africa. D.M. ANDERSON and M.L. COX, Systematic Entomology Laboratory, USDA, Washington DC, USA.

Abstract - The taxonomy of three species of Smicronyx that are potential biological control agents of Striga spp. in West Africa is revised. The two most abundant species are identified as Smicronyx (Afrosmicronyx) umbrinus Hustache and Smicronyx (Smicronyx) guineanus Voss. A third species is described as Smicronyx (Afrosmicronyx) dorsomaculatus Cox, sp.n. Diagnostic descriptions and a key, to separate adults of the three species from each other and from Sharpia bella, are presented. Mature larvae of the three Smicronyx species are separated through a key and diagnoses. A lectotype is selected for S. umbrinus. All available host and distribution data are summarized for each species.

Automating the identification of insects: a new solution to an old problem. P.J.D. WEEKS, I.D. GAULD, K.J. GASTON and M.A. O'NEILL, Department of Entomology, The Natural History Museum, London, UK.

Abstract - A semi-automated digital image analysis system capable of discriminating five closely related species of Ichneumonidae is described. Specimens were distinguished by differences in their wings. The system functions by (a) extracting the significant variation (principal components) among a training set of images of the same species, (b) using these principal components to represent efficiently the morphology of wings of that species, and (c) exploiting the fact that images of the same species will share characteristic principal components, while images of different species will not. Such an approach allows the construction of modular species classifiers, to which like species correlate strongly, while dissimilar species do not. A recognition accuracy of 94% was achieved when the system was tested on 175 images of wings of the five ichneumonids. The wing images were caricatured to accentuate their venation and pigmentation patterns.