Abstract
Despite a wealth of evidence demonstrating extraordinary maximal performance, little is known about the routine flight performance of insects. We present a set of techniques for benchmarking performance characteristics of insects in free flight, demonstrated using a model species, and comment on the significance of the performance observed. Free-flying blowflies (Calliphora vicina) were filmed inside a novel mirrored arena comprising a large (1.6 m1.6 m1.6 m) corner-cube reflector using a single high-speed digital video camera (250 or 500 fps). This arrangement permitted accurate reconstruction of the flies' 3-dimensional trajectories without the need for synchronisation hardware, by virtue of the multiple reflections of a subject within the arena. Image sequences were analysed using custom-written automated tracking software, and processed using a self-calibrating bundle adjustment procedure to determine the subject's instantaneous 3-dimensional position. We illustrate our method by using these trajectory data to benchmark the routine flight performance envelope of our flies. Flight speeds were most commonly observed between 1.2 ms−1 and 2.3 ms−1, with a maximum of 2.5 ms−1. Our flies tended to dive faster than they climbed, with a maximum descent rate (−2.4 ms−1) almost double the maximum climb rate (1.2 ms−1). Modal turn rate was around 240°s−1, with maximal rates in excess of 1700°s−1. We used the maximal flight performance we observed during normal flight to construct notional physical limits on the blowfly flight envelope, and used the distribution of observations within that notional envelope to postulate behavioural preferences or physiological and anatomical constraints. The flight trajectories we recorded were never steady: rather they were constantly accelerating or decelerating, with maximum tangential accelerations and maximum centripetal accelerations on the order of 3 g.
Highlights
Insects achieve remarkable flight performance, and the literature is replete with observations and measurements to prove this: from the astonishing prey capture rates of darter dragonflies [1] to the 4500us21 angular velocities achieved by courting dolichopodid flies [2]
Perhaps the most sophisticated camera system used to investigate insect flight to date is that developed by Fry and colleagues [6,7], which uses paired pan-tilt cameras to obtain high resolution images of small insects flying in a large volume
Performance Envelope The various components of flight performance described in the previous section are not expected to be maximised simultaneously
Summary
Insects achieve remarkable flight performance, and the literature is replete with observations and measurements to prove this: from the astonishing prey capture rates of darter dragonflies (up to 98%) [1] to the 4500us angular velocities achieved by courting dolichopodid flies [2]. Previous studies have tracked insects using a variety of techniques, from simple single camera systems, which assume approximately 2-dimensional motion [4,5] to sophisticated tracking camera systems [6,7], onboard transponders for harmonic radar experiments [8,9] and onboard electromagnetic search coils [10,11,12]. Such systems have been used most commonly in the lab, Dahmen and Zeil [13] developed a method for using synchronised 16 mm film cameras in the field (demonstrated by mapping the trajectories of a lesser housefly, Fannia cannicularis, patrolling the airspace beneath a lamp shade). Perhaps the most sophisticated camera system used to investigate insect flight to date is that developed by Fry and colleagues [6,7], which uses paired pan-tilt cameras to obtain high resolution images of small insects flying in a large volume
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