PROC. ENTOMOL. SOC. WASH. 93(3), 1991, pp. 737-747 SENSILLA ON THE ANTENNAE, FORETARSI AND PALPI OF MICROPLITIS CROCEIPES (CRESSON) (HYMENOPTERA: BRACONIDAE) R. C. Navasero and G. W. Elzen (RCN) Assistant Entomologist, Department of Entomology, Drawer EM, Mississippi State University, Mississippi State, Mississippi 39862; (GWE) Research Entomologist, USDA-ARS, Southern Field Crop Insect Management Laboratory, P.O. Box 346, Stone-ville, Mississippi 39776. Abstract. —Stnsovy receptors on the antennae, labial and maxillary palpi, and foretarsi of Microplitis croceipes (Cresson) were examined by scanning electron microscopy. The occurrence of antennal sensilla not described by earlier workers is reported. Generally, there are 6 types of sensilla in adults of M. croceipes, namely, sensilla (s.) trichodea, s. basiconica, s. chaetica, s. placodea, s. campaniformia and s. coeloconica. Sensilla placodea, campaniformia and coeloconica occur only on antennal flagella. However, s. trichodea and s. basiconica were present on all structural parts examined. Variants of s. trichodea (Trichodea A, B, C and D) and those of s. basiconica (Basiconica A and B) are described. The present paper documents for the first time the occurrence of Trichodea B, C and D, Basiconica B, s. chaetica, s. campaniformia and s. coeloconica in M croceipes. Sexual dimorphism in M. croceipes correlates with antennal sensilla type; s. campaniformia are present only on female antennae whereas s. coeloconica and bent-tipped trichoid sensilla (D) occur only on male antennae. Other sensilla types occur in both sexes. Key Words: Sensilla, antennae, foretarsi, labial palps, maxillary palps, sexual dimor-phism Insects are generally heavily vested with Gupta 1981). Sensory organs on the mouth-hairs (sensilla) used for olfactory, gustatory, parts and tarsi have been found to influence hygro-, mechano-, and thermo-reception feeding in Phormia, Tahanus, Locusta and (Ramaswamy and Gupta 1981). The re-Chrysomela species, whereas those on the sponses of various sensilla may vary with tarsi of Pieris brassicae (L.), Delia brassicae insect structural parts (O'Connel 1975), be-Bouche, Psila rosae (F.), Rhagoletis sp. and tween insects (Dethier 1977), gender and Ceratitis sp. are involved in oviposition age after ecdysis, or emergence (Zacharuk (Stadler 1980). Antennal sensory receptors 1980). Detection of chemotactic stimuli by in parasitic wasps play an important role in insects is mediated by sensory receptors host choice, including detection of ovipo-present on the antennae, mouthparts, and sitional and host recognition cues (Weseloh tarsi (Frings and Frings 1949, Weseloh 1972, Barlin and Vinson 1981). Insects may 1972). In Blatella germanica (L.) phero-also rely on chemoreceptors found on the mone detection is mediated by sensory re-labial and maxillary palpi in addition to ceptors on the antennae and on the maxil-those found on the antennae in perceiving lary and labial palps (Ramaswamy and host plant chemicals, as in Choristoneura
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