Taxonomy, Life History, and Ecology of a Mountain-Mahogany Defoliator, Stamnodes animata (Pearsall), in Nevada,

During 1978-79, larvae of a geometrid moth, Stamnodes animata Pearsall, defoliated curlleaf mountain-mahogany Cercocarpus ledifolius Nutt. on 4,500 ha at Sheldon Wildlife Refuge, Washoe and Humboldt Counties, Nevada. Extensive tree mortality resulted. The genus Stamnodes Guenee is partly revised herein, and animata is transferred to it from Marmopteryx Packard. Life stages and their habits are described. Moths were present from late May to mid-July, with oviposition commencing in early June. Larvae were present from June until October and began descending to pupate in soil in late September. Population sampling is discussed. Eggs were parasitized by three species of wasps Telonomus sp., Trichogramma pretiosum Riley, T. exiguum Pinto and Platner. Larvae were parasitized by an ichneumon wasp probably Netelia sp. and by two tachinid flies, Patelloa plumisenata A W and Blondelia connecta Curran. Predacious tree-climbing ants Formica integroides planipilis Creighton played a major role in the much greater survival of mountain-mahogany at higher elevations than at lower areas, where gound-dwelling harvester ants Pogonomyrmex owyheei Cole were dominant. Densities of 10 key site-indicator species of passerine birds on defoliated transects are compared before defoliation and for 6 years afterward. Where tree killing was greater, bird densities fluctuated more, and two species-the gray flycatcher Empidonax wrightii and American robin Turdus migratorius-disappeared. Litter weight was 1,186 gm2 greater under defoliated than nondefoliated trees because of premature loss of looper-notched leaves. Susceptible stands are extensive in area grow on litter-rich permeable soil and lack Formica ants.