Bulletin of Entomological Research (2002) 92, 165–175 DOI: 10.1079/BER2001144 Morphometric and molecular analysis of the Encarsia inaron species-group (Hymenoptera: Aphelinidae), parasitoids of whiteflies (Hemiptera: Aleyrodidae) S. Manzari 1,3 , A. Polaszek 1,2 * , R. Belshaw 1 and D.L.J. Quicke 1,2 1 Department of Biological Sciences, Imperial College of Science, Technology and Medicine, Silwood Park, Ascot, Berkshire, SL5 7PY, UK: 2 Department of Entomology, The Natural History Museum, Cromwell Road, London, SW7 5BD, UK: 3 Department of Insect Taxonomy Research, Plant Pests and Diseases Research Institute, PO Box 1454, Tehran 19395, Iran Abstract Several series of host-reared specimens of an Encarsia species, initially thought to be the cosmopolitan Encarsia inaron (Walker), were collected in the Azores Islands (Portugal). Subsequent morphometric analysis supported the presence of two species: E. inaron and a new species, described herein as Encarsia estrellae Manzari & Polaszek sp. n. Encarsia estrellae was reared from Aleyrodes singularis Danzig, A. ?singularis, and Bemisia sp. afer-group on several host plants. In addition, the D2 region of the 28S rDNA gene was sequenced in eight individuals belonging to these species, as well as single representatives of two closely related and one distantly related species. Phylogenetic analysis of these DNA sequences, together with 23 additional Encarsia sequences retrieved from the European Molecular Biology Laboratory (EMBL) and GenBank databases, further supported the specific status of E. estrellae, and the placement of E. dichroa (Mercet) in the E. inaron species-group. Additionally, E. inaron is redescribed and some taxonomic problems in the E. inaron species-group are discussed. Introduction Encarsia Förster (Hymenoptera: Aphelinidae) is a taxonomically difficult genus, which currently contains about 280 described species (Polaszek et al., 1999). Encarsia species are mostly primary parasitoids of whiteflies (Hemiptera: Aleyrodidae) and armoured scale insects (Hemiptera: Diaspididae) – on which they are important biological control agents – (Huang & Polaszek, 1998), but four species are parasitoids of aphids (Hemiptera: Aphididae: Hormaphidinae) (Evans et al., 1995) and a few species parasitize the eggs of Lepidoptera (Polaszek, 1991). Although recent papers (Viggiani, 1985, 1987; Hayat, 1989, 1998; Polaszek et al., 1992, 1999; Evans & Polaszek, 1998; Huang & Polaszek, 1998) have contributed to the identification of these parasitoids, reliable identification is still difficult for many species. This is for several reasons, e.g. their small size, diversity, and the existence of complexes of morphologically indistinguishable or hard to distinguish species (Polaszek et al., 1999). The assignment of species- groups to Encarsia and the placement of the species within species-groups is also problematic, and a revision of the genus on a world basis is needed (Hayat, 1998). Approximately 29 species-groups are currently recognized *Author for correspondence Fax: +44 (0)20 759 42339 E-mail: a.polaszek@ic.ac.uk