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(a) Field thoracic temperature

(a) Field thoracic temperature

Thoracic temperature (°C)

Figure 6.5 Vertical force production of (a) teneral and (b) mature dragonflies (Libellula pulchella) as a function of thoracic temperature.

Note: Grouping the dragonflies into age classes shows that the thermal sensitivity curve narrows and performance increases with maturation. Field thoracic temperatures are compared with optimal thoracic temperatures: horizontal bars show the mean (vertical line near centre) ±SD (thick bar) and range (thin bar).

Thoracic temperature (°C)

Figure 6.5 Vertical force production of (a) teneral and (b) mature dragonflies (Libellula pulchella) as a function of thoracic temperature.

Note: Grouping the dragonflies into age classes shows that the thermal sensitivity curve narrows and performance increases with maturation. Field thoracic temperatures are compared with optimal thoracic temperatures: horizontal bars show the mean (vertical line near centre) ±SD (thick bar) and range (thin bar).

of muscle physiology in dragonflies is a superb integrative analysis extending across all levels of biological organization from ecology and flight performance through to cellular and now molecular mechanisms (for review see Marden et al. 1998). Marden et al. (1996) assumes that endothermic warming is the most derived condition in dragon-flies, and that evolution of endothermy was probably preceded by selection on the thermal sensitivity of performance. A phylogenetic distinction between ectothermic perchers (Libellulidae) and endothermic fliers (Aeschnidae) was made by Heinrich and Casey (1978), but does not hold for all dragonflies, and the dichotomy between

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