Gross morphology of multiporous plate sensilla in the Hymenoptera (Insecta) HASAN H. BASIBUYUK &DONALD L. J. QUICKE Accepted 17 December 1998 Basibuyuk, H. H. & Quicke, D. L. J. (1999). Gross morphology of multiporous plate sensilla in the Hymenoptera (Insecta). Ð Zoologica Scripta 28, 51±67. Both external and internal gross morphology of multiporous plate sensilla were investigated throughout the Hymenoptera, with particular reference to nonaculeate families, using SEM. Several scenarios concerning the origin of multiporous plate sensilla are discussed. Shape, attachment, position, and reinforcing structures, were found to vary between the families, and the possible phylogenetic implications of these are discussed. Hasan H. Basibuyuk, Unit of Parasitoid Systematics, CABI Bioscience UK Centre (Ascot), Department of Biology, Imperial College at Silwood Park, Ascot, Berkshire, SL5 7PY UK, Department of Entomology, The Natural History Museum, London, SW7 5BD UK, and Department of Biology, Cumhuriyet University, 58140-Sivas, Turkey. E-mail: H.basibuyuk@nhm.ac.uk Donald L. J. Quicke, Unit of Parasitoid Systematics, CABI Bioscience UK Centre (Ascot), Department of Biology, Imperial College at Silwood Park, Ascot, Berkshire SL5 7PY UK, and Department of Entomology, The Natural History Museum, London, SW7. Introduction Interest in using sensilla morphology as a source of infor- mation for phylogenetic evaluation of the Hymenoptera is not new, but it has only recently been put into practice. One of the earliest authors to realize the importance of this complex character system was Bo È rner (1919) who used the shape of `sensilla placodea' in his classi®cation of the order. Walther (1981, 1983, 1985) discussed the possible value of the `patterns of sensilla' for phylogeny reconstruc- tion. His ®ndings suggested that the density, distribution, morphology and ultrastructure of sensilla could be infor- mative concerning the problem of the still unknown common ancestor of the ants as well as of the relationships of other Hymenoptera; he also noted that the patterns of antennal sensilla are highly complex and include a number of variable subcharacters. Barlin & Vinson (1981a) compared ratios of aperture length to sensillar plate length in some braconid wasps for potential use in braconid systematics and this was subsequently included in the phylogenetic analysis of Quicke (1994) and Quicke et al. (1999). Gibson (1986) found that the external structure of multiporous plate sensilla (MPS) provided evidence for a relationship between the Mymaridae and the rest of Chal- cidoidea excluding Mymarommatidae. The general trend thus has been to study sensilla in particular groups of Hymenoptera rather than across the whole order. Interpre- tation of these studies is further complicated because the terminology used has been inconsistent (Barlin & Vinson 1981b). MPS were ®rst designated as `pore plates' by Leydig (1860) and Kra Èpelin (1883), and their presence is often mentioned in taxonomic descriptions. They have been variously known as `sensilla placodea' (i.e. Schenk 1903; Snodgrass 1926; Slifer et al. 1964; Richerson et al. 1972), `rhinaria' (e.g. Richards 1977) or `elongate placoid sensilla' (Borden et al. 1978a,b). All these terms are rather ambigu- ous and do not describe the precise structure of the plate of the sensilla. In recent literature, however, they have been more consistently referred to as the multiporous plate sensilla (MPS) (e.g. Barlin 1978; Barlin & Vinson 1981a,b; Frazier 1985). In addition to having pores, Zacharuk (1980, 1985) drew attention to the pitted or grooved surface of these chemosensilla, and accordingly the term `multiporous pitted plate sensilla' (MPP) was recom- mended as it seems to best describe the general morphol- ogy of the structure. This feature of the plate can only be determined using SEM, and it usually requires special preparation of the specimen for high magni®cation work. Therefore, it is not possible in most cases to differentiate `pitted' and `grooved' multiporous plate sensilla. The more general term multiporous plate sensilla (MPS) is therefore used in this study. An excellent SEM study by Olson & Andow (1993) has proved that it is possible to obtain high resolution scanning electron micrographs of MPS, even in Q The Norwegian Academy of Science and Letters . Zoologica Scripta, 28, 1±2, 1999, pp51±67 51