PROC. ENTOMOL. SOC. WASH. 91(3), 1989, pp. 325-341 TAXONOMIC STUDY OF THE LARVAE OF SIX EASTERN NORTH AMERICAN DIORYCTRIA (LEPIDOPTERA: PYRALIDAE: PHYCITINAE) Nancy Antoine Leidy and H. H. Neunzig Department of Entomology, North Carolina State University, Raleigh, North Carolina 27695-7613. Abstract.— Larvae of six eastern North American species of Dioryctria Zeller were examined using both a stereo light microscope and a scanning electron microscope (SEM). Detailed descriptions and a key to the species, supplemented with electron micrographs, are presented for the last instar larvae of D. ahietivorella (Grote), D. disclusa Heinrich, D. pygmaeella Ragonot, D. clarioralis (Walker), D. amatella (Hulst), and D. taedivorella Neunzig and Leidy. Key Words: Pyralidae, Phycitinae, Dioryctria, immatures, coneworm, taxonomy The genus Dioryctria Zeller is mostly Holarctic in distribution with a few species also occurring in the northern tropics. Fif-teen species are known from eastern North America. Larvae feed exclusively on coni-fers. The adults of the North American species of Diorycia have been the subject of exten-sive taxonomic study beginning with Hein-rich (1956) and Munroe (1959). In 1969, Mutuura, working in conjunction with sev-eral others, began a series of papers follow-ing up on Munroe's work (Mutuura, Mun-roe and Ross 1 969a, b, Mutuura and Munroe 1972, 1973. 1974, 1979, Mutuura 1982, Mutuura and Neunzig 1986). Additional work on the adults has been done by Scha-ber and Wood ( 1 97 l),Coulsonetal.'( 1972), Blanchard and Knudson (1983) and Neun-zig and Leidy (1989). Although Dioryctria larvae have been briefly covered in various publications on forest pests, detailed descriptions of the lar-vae are few. MacKay (1943) described and figured the lar\ae of D. reniciilcllnides Mu-tuura and Munroe (as D. rcniculella Grote), and briefly diflerentiated it from D. ahieti-vorella (Grote) (as D. abietella Denis and SchiflTermuUer). Farrier and Tauber (1953) described and illustrated the larvae of D. disclusa Heinrich, and Lyons (1957) also described D. disclusa as well as D. cambi-icola (Dyar) and D. ahietivorella (as D. abie-tella). Neunzig et al. (1964), gave detailed descriptions of six species occurring in the southeastern United States: D. amatella (Hulst), D. eheli Mutuura and Munroe (as D. abietella), D. clarioralis (Walker), D. dis-clusa. D. taedivorella Neunzig and Leidy (as D. ziinmermani (Grote). and D. pygmaeella Ragonot. Schaber (1981) published on the larvae of D. taedae Schaber and Wood, however, larvae of D. taedivorella and D. yalesi Mutuura and Munroe were probably included in the described material. Only two studies of Dioryctria have made use of scanning electron microscopy (SEM). Bradley et al. (1982) used SEM to examine the eggs of three species, D. disclusa. D. amatella and D. eheli. The early-instar lar-vae of D. reiiiculelloides were examined by Spies and Dimond using SEM (1985).