PROC. ENTOMOL. SOC. WASH. 88(4), 1986, pp. 666-672 A DESCRIPTION OF THE LATE-INSTAR LARVA OF XENOMYCETES LA VERSI HATCH (COLEOPTERA: ENDOMYCHIDAE) WITH NOTES ON THE SPECIES' HOST AND DISTRIBUTION Paul J. Johnson Department of Plant, Soil and Entomological Sciences, University of Idaho, Moscow, Idaho 83843. Abstract. — The late-instar larva of Xenomycetes laversi Hatch is described for the first time. SEM illustrations are presented to show unusual mycangial setae. Paxillus atrotomentosus (Batsch ex. Fr.) Fries is apparently the sole fungal host for both adults and larvae of the beetle. New collection data are presented for the species' known range in Washington and Oregon (New State Record). Xenomycetes laversi Hatch was originally described from two specimens labelled "Seattle, Wash" (Hatch, 1961). Since this description, few specimens of this beetle have appeared in collections and no reports of it have been published. Here, I describe the late instar larva, identify the apparent sole host fungus, and report additional collections from various localities in western Oregon and Washington. Larvae of six genera of Endomychidae found in North America have been described or illustrated. Boving and Craighead (1931) illustrated and gave key characters for Mycetaea hirta Marsham, Aphorista vittata (Fabricius), Stenotarsus hispidus Herbst, Endomychus cocci neus Linnaeus., E. biguttatus Say, Lycoperdina ferruginea LeConte, and Rhymbus ulkei Crotch. Peterson (1960) provided illus-trations of and a family description based on L. ferruginea and E. biguttatus. Pakaluk (1984) presented a description of the larva of L. ferruginea along with extensive biological data. The following description is based on specimens which were killed in 70% ethyl alcohol, and preserved in a 19:1 solution of 70% ethyl alcohol and glycerin. Specimen preparation for SEM began with decapitation and a soaking in warm 1 N NaOH for 10-15 minutes. Specimens were then rinsed and flushed with distilled water, fixed with a solution of 2% glutaraldehyde in 0. 1 M sodium phosphate, buffered, and dehydrated in a graduated series of ethyl alcohol. Spec-imens were then critical point dried, attached to stubs with double-stick cellophane tape, ion-coated with gold-palladium, and examined with an ISI-60 scanning electron microscope at 30 kv. Xenomycetes laversi Hatch Late instar larva. — Length 7.0 mm, width 1.8 mm, turgid; onisciform, broadly fusiform in dorsal aspect; shallowly convex dorsally; flavotestaceous, coriaceous, with sparsely to moderately distributed, erect, basket-like mycangial setae (Figs. 1 , 3), marginal bristles slightly longer than discal bristles; densely set with truncate
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