Comparative Thermoregulation of Four Montane Butterflies of Different Mass

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Abstract
In this field study, I examine whether body mass affects flight behavior and thoracic temperature ( ) in butterflies from a relatively cool environment (3,100 m high in the Sierra Nevada of California). Comparisons are made with thermoregulatory patterns of butterflies from other habitats and are discussed in terms of male mating strategies. The smallest (.023 g) butterflies examined (males ofAgriades glandon) spent 94% of the time in the morning basking and 6% flying. Near noon, they spent only 25% of the time perched (basking). Agriades glandon did not regulate a stable . Instead, these small butterflies prolonged flight duration by storing heat prior to flight; the was on the average 9.2 C higher at takeoff than at landing. Almost all A. glandon basked dorsally near midday. However, a large percentage, 30% in the morning and 60% in the evening, basked laterally. Heating rates in the field were indistinguishable between lateral and dorsal basking positions in recently killed A. glandon and Nymphalis antiopa. Basking posture may be related to visual vigilance. Occidryas editha regulated at 36-37 C, and takeoff and postflight were indistinguishable. These butterflies continued to remain perched and ready to chase conspecifics after attaining a suitable for flight, and they regulated while perched by adjusting wing positioning. Nymphalis antiopa, the largest butterfly (.313 g) examined, maintained its Similar to that of others that were as much as 25 times lower in mass. The Of the montane butterflies were similar to those of similar body mass and wing loading from two other habitats. Morphology appears to play the major role in determining in the absence of compensating mechanisms, and different behaviors are used to achieve specific in thermally diverse environments.