Comparative Thermoregulation of Four Montane Butterflies of Different Mass

Abstract

In this field study, I examine whether body mass affects flight behavior and thoracic temperature ($T_{th}$) 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 $T_{th}$. Instead, these small butterflies prolonged flight duration by storing heat prior to flight; the $T_{th}$ 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. g...