Milbert's Tortoiseshell, Aglais milberti (Lepidoptera: Nymphalidae): a facultative trogloxene in alpine caves

We have recently completed a bioinventory of caves of Great Basin National Park (White Pine County, Nevada) in which we observed and collected butterflies in two caves located above timberline. In Mountain View Cave (length 16.2 meters, elevation 3413 meters), two specimens of A. milberti were collected on 18 July 2007 from dry bedrock ceiling in the twilight zone, where the temperature was between 2.07 and 15.57 ○C, the relative humidity was between 34.6 and 80.9%, and light was less than 4 lux (the collection was between two stations where the parameters were measured, thus a range is given). Surface conditions were 20.39 ○C, 25.9% relative humidity, and light 94600 lux. In Broken Cave (length 32.9 meters, elevation 3407 meters), one specimen of Milbertʼs Tortoiseshell was collected on 10 July on a dry rock wall and another on 16 July 2007 on a dry bedrock ceiling (Figure 1), with others observed on 16 July 2007.