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First published online March 30, 2006
Journal of Experimental Biology 209, 1430-1440 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02132

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Wind generated by an attacking bat: anemometric measurements and detection by the praying mantis cercal system

Jeffrey D. Triblehorn^* and David D. Yager

Department of Psychology, University of Maryland, College Park, MD 20742, USA

View larger version (42K): [in a new window]   Fig. 1. (A) Schematic of the flight room setup for the physiological experiments, viewed from above. The gray region represents the high-speed video-system's calibrated area for distance measurements. The dark circle marks the location of the mantis during the experiments. (B) Photo of a trial during the anemometer measurements of bat-generated wind. The anemometer probe sits inside the protective cage except for the sensor region positioned about 3 cm outside the top of the cage. In the photo, the sensor sits 24 cm below the mealworm target (inside circle) as the flying bat approaches the target just before capturing it. The photo is from Camera 2 (A) of the high-speed video system.

View larger version (32K): [in a new window]   Fig. 2. Implanted electrode recordings of wind-sensitive interneuron activity in the abdominal connective of a mantis. (A) Neural activity from the mantis recorded while blowing on the cerci (top) and just before the bat captured the mantis (bottom). The similarity between the two responses indicates that both traces result from wind-sensitive interneuron activity. Scale bars: 200 mV, 50 ms. (B) Same trial (shaded area in A) viewed on an expanded time scale. Scale bars: 200 mV, 20 ms.

View larger version (25K): [in a new window]   Fig. 3. Five examples of abdominal connective activity recorded by an implanted electrode during the last 280 ms before a flying, attacking bat captured the mantis. Arrows mark the beginning of the response in each trial and the numbers state the time (distance) that the response began before capture. The examples illustrate that wind-related activity evoked by the bat's approach was characterized by a sudden increase in neural activity that was sustained until the bat captured the mantis. Scale bars: 100 mV, 25 ms.

View larger version (17K): [in a new window]   Fig. 4. Histograms of times (A) and distances (B) before capture when wind-sensitive interneuron activity began during flying bat attacks.

View larger version (10K): [in a new window]   Fig. 5. Anemometer output from a single trial where the probe was placed 2 cm from the mealworm target. Contact occurred as the wind velocity continued to increase, but possibly before the wind velocity reached its peak. Scale bars: 50 cm s–1, 50 ms.

View larger version (23K): [in a new window]   Fig. 6. Anemometer traces of wind generated by an attacking bat as it approaches a mealworm target, captures it, and flies away. Since the anemometer was not directly at the target's location, contact times (arrows) for each trace were predicted based on the one trial when the anemometer was located at the target (see Fig. 7). The examples illustrate the major changes in the anemometer traces as peak velocities increase; see text for details. The anemometer traces indicate that the bat generates a short but strong stimulus as it approaches and captures the target and a longer but weaker stimulus follows as the bat flies away. Scale bars: 50 cm s–1, 500 ms.

View larger version (19K): [in a new window]   Fig. 7. (A) Peak wind velocities measured by the anemometer at distances 20–60 cm from the target (N=94). The anemometer was within 18–30 cm of the target in 77% of the trials. The shaded boxes indicate the percentage of measured peak wind velocities that fell between 0–49, 50–99 and >100 cm s–1 for the data collected with the anemometer within 20–30 cm of the target only. (B) Distribution of peak accelerations for 66 of the trials in A. Peak acceleration was calculated using the onset time of the anemometer detecting the bat-generated wind to the time of the peak velocity. (C) Comparison of peak velocity and peak acceleration for each trial in B. For bat-generated wind, peak velocity and peak acceleration were closely related, with peak acceleration increasing exponentially with increasing peak velocity. The equation for the exponential best fit line is f(x)=4.980398x10–1*exp(4.814839x10–2*x).