LIQUID ASSETS FOR FAT BANKERS - SUMMER NECTARIVORY BY MIGRATORY MOTHSIN THE ROCKY-MOUNTAINS, COLORADO, USA

Fat accumulation and delays in reproduction have been documented for v arious migratory vertebrates. To examine this phenomenon in insects, w e chose migratory and nonmigratory moths. Three species of Noctuidae w ere compared for accumulation of abdominal fat during their periods of activity in the alpine zone of the Rocky Mountains of Colorado from 1 978 to 1980. Euxoa auxilliaris is a Class II migrant that enters the a lpine zone from the plains in early summer. There it feeds on floral n ectar of many species of plants and accumulates neutral fat reserves i n the abdomen. These fat reserves start at 13-46%, in late June, and r ise to 72-85%, by the end of August and early September, when the moth s leave the area. The moths do not aestivate (i.e. enter imaginal diap ause far the summer), but are in reproductive diapause throughout the alpine summer. Almost no females have maturing ovaries even by August. Resident moths, E. lewisi and Lasiestra impingens curta, do not show reproductive diapause and do net accumulate fat.