The operative muscle temperature and contraction kinetics are described for
the endothermic cicada Tibicen winnemanna (Davis). Measurements of timbal
muscle temperature in the field demonstrate that timbal muscle temperature
is elevated above ambient temperature during activity. Timbal muscle temper
ature increases as the acoustic output progresses from a 'warm-up' buzz (27
.9-29.7 degreesC) to full song production (36.3-39.5 degrees). Mean muscle-
ambient temperature difference increases from 5.8 degreesC in buzzing anima
ls to 13.1 degreesC in animals producing a full calling song. Twitch rise t
ime and onset to 50% relaxation time decrease while tension production incr
eases with increasing temperature to 40 degreesC. Mean force production at
20 degreesC was determined to be 0.22 +/-0.06 N/cm(2), The characteristics
of T. winnemanna muscle are similar to those reported in other cicada speci
es. Analysis of the songs produced by animals with one timbal destroyed and
the sounds produced by mechanical manipulation suggest that the timbals al
ternately contract and relax in the sequence IN1-IN2-OUT1-OUT2. Measurement
s of the inferred period of muscle contraction from song recordings and the
contraction kinetics of isolated timbal muscles measured in the laboratory
show that the temperature of the timbal muscle must be elevated in order f
or the cicada to be able to produce the calling song. (C) 2001 Elsevier Sci
ence Inc. All rights reserved.