The larvae of the range crane fly (Tipuh simplex) are responsible for extensive damage to rangelrnd of the central valley of California, but the damage occurs infrequently in years when there are extremely high densities. These outbreaks appear to be due to favorable climatic conditions during the early larval instars. Means of biological (including pheromone), mechanical, fue, and chemical control are discussed. Early detection is a key in minimizing damage. The California annual rangeland provides substantial quantities of forage for cattle during fall, winter, and spring. Annual grasses and forbs dominate this range type. Vegetation starts growing with the advent of fall and winter tsrinc usruallv mntlwinrr hv _A_nril nr _ _ _ _ __, , ____ ___ .__~ 1, r---May in some years. An event which coincides with the fall rain is the breaking of diapause and eventual hatching of the eggs of the range crane fly (Tipulu simplex Doane). The range crane fly is one of the most destructive species to rangeland in California (Essig 1958). It has a known California distribution from northern Santa Cruz County, north to Marin County, and east to Sacramento County. A second, discontinuous population is found in the Yokohl Valley of Tulare County (Alexander 1967). During the winter of 1977-78, a third ~:___-r:_.._.._ <_-..,_r:..__.^^ _..‘___1_~ :_ T-L_-_ #?-.._... -.l_:_l_ uIsC”IIIIn”“llS popurarlon was rec”r”eo m 1 enama Loumy, wnrcn was confirmed by the authors (Fig. I). Unconfirmed reports indicate that the range crane fly may also occur in Oregon, east of the Cascade Mountains. In California, the suitable habitat appears to be the unirrigated pastures of the central valley of California, below the oak-woodland zone. Crane fly larvae feed on decaying matter in the soil, cowpads which are at least one season old, and roots of range forage plants. Infrequently (about once every 6 years in Tulare County), the larvae reach such high concentrations that they destroy all forage, denude hills, and cause adverse effects on the watershed (Fig. 2). This condition has in the past been confused with localized overgrazing. Fig. 1. Runge of Tipula simplex in Cal~$orn~. The present paper reports on the effects of the range crane fly on rangeland in Tulare County, California, and possible control measures. The study area in Yokohl Valley is located approximately 11 km southeast of Exeter, California. Elevation ranges from 150 to 305 m above sea level. Topography is rolling with many small drainAuthors are with the Biology Department, Californ/a State University,Los Angeles !33;$ and the Tulare County Agrwltural Commtsstoners Office, Vtsaha, Cahf. The authors would like to thank the Boston Land Company and CSULA for financial support of this project, and Mr. William Clark and Dr. Robert Zahary for their comments on the project and their critical reading of the paper. We would also like to thank L. Gholson, CD. Hynes, N. Mosman, and J. Suffleet for their collaboration in various aspects of data gathering and analysis. ages dissecting the area. The overall study area is generally on level-to-gently sloping alluvial soils with the slope usually not exceeding 5 to 6%. Soils of the area are both alluvial and upland (Storie et al. 1940) derived dominantly from basic igneous parent material with the upper surfaces displaying slightly acidic qualities. Annual precipitation ranges from 304 mm to 633 mm with 85% occurring between November and April (State of California Department of Water Resources, 1955-60). The mean annual ambient temperature is 16O C with extremes ranging from 8” C to 47O C (U.S. Weather Bureau, 1960-76). Four sites were studied. Two sites wem relatively flat, the third site was a hillside with a southern exposure, and the fourth was a hillside with a northern exposure. All sites have similar vegetation surface in response to orthodichloro-benzene (Barnes 1941). This is ineffective on the range crane fly.