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Fig. 1. Muscle preparation for work loop measurements. (A) Placement of the
anterior (a) and posterior (p) muscle grips for force measurements on
mechanically isolated muscles. (B) After decapitating the moth, the 1st
phragma was exposed and the anterior grip placed over the anterior insertion
of the dl1 muscles. The paired needles of the posterior grip were
driven through the dorsal cuticle and down along the posterior face of the 2nd
phragma. Both grips were secured to the exoskeleton with cyanoacrylate
adhesive. After gluing acetate strips (not shown) across the gap between the
two grips to fix their relative positions, cuticle strips were excised
(arrows, broken line) to mechanically isolate the anterior grip and muscle
insertions from the rest of the thorax. The anterior grip was then secured to
the force transducer via the treaded rod projecting from the grip.
The ball bearing (bb) mounted on the posterior grip fit into a depression in
the end of a threaded rod (tr) mounted on a magnetic coil oscillator. When
secured by a slotted retaining nut (n), the ball bearing and threaded rod
formed a ball joint. The acetate strips spanning the two grips then were cut,
and any misalignment of the cut ends was corrected using the ball joint and
oscillator. a–e, dl1 muscle subunits.
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