Energetics of locomotion in endothermic insects.

Abstract

Endothermic insects are those adult members of several insect orders that rely upon internally produced heat to regulate body temperature (31, 53). Known endotherms include some dragonBies (Odonata) (21, 53), a few katydids (Orthoptera) (30, 43), some flies (Diptera) (51), many bees and wasps (Hymenoptera) (25, 32-34, 49), some beetles (Coleoptera) (11, 36, 37, 53, 58), many moths (6, 8-10, 15, 16, 29, 31) and some butterflies (64) (Lepidoptera), and some owl Bies (Neuroptera) (51). These animals are among the largest of their kind, > 100 mg (6), and have insulation to decrease the rate of heat loss from the thorax (1, 6, 9). They generate and conserve heat during flight and possess special warm-up behavior patterns to elevate thoracic temperature prior to critical stages of activity (45, 46). Endothermic insects both walk and By. Walking is a relatively inexpen­ sive process, but Bight makes enormous demands on the muscle system. Many of these insects are capable of sustained hovering, which is probably the most energetic biological process known; it is near the upper theoretical limit for power generation by striated muscle (2, 43, 79). A few insects have developed dependence on the heat production of Bight muscles for functions other than Bight, such as warm-up prior to and during singing (22, 30, 69) and regulation of nest temperature (49, 68). Comprehensive reviews of temperature regulation (53) and endothermy (31) in insects, Bight energetics (46) and locomotion (41, 62) in insects, and related topics (21), and recent symposia and books (4, 14, 33, 35, 61, 63, 66, 82) deal with many aspects of our topic. We focus on the current understanding of the cost of locomotion in insects and refer to the older literature only where necessary to clarify the present position.