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First published online February 4, 2005
Journal of Experimental Biology 208, 721-735 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01418

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Odor-modulated orientation in walking male cockroaches Periplaneta americana, and the effects of odor plumes of different structure

M. A. Willis^* and J. L. Avondet

Department of Biology, Case Western Reserve University, Cleveland, OH 44106-7080, USA

View larger version (32K): [in a new window]   Fig. 1. (Ai-Di) Time-averaged plume boundaries of titanium tetrachloride smoke plume in 25 cm s-1 wind as viewed from above. (Ai) Point-source plume, 2.4 cm wide at the source, spreads to 7.7 cm wide at the downwind end. (Bi) Ribbon plume, 1.5 cm wide at the source, spreads to 6.1 cm wide at the downwind end. (Ci) Wide plume, 17 cm wide at the source, spreads to 26.5 cm at the downwind end. (Di) Cylinder plume, 7.6 cm wide at the source, spreads to 68.1 cm at the downwind end. In this figure, wind flows from left to right. Schematic illustrations of the pheromone sources are depicted at the upwind end of each plume envelope. Broken rectangles represent the boundaries of the experimental arena. (Aii-Dii) Vertical cross-section of time-averaged plume boundaries of titanium tetrachloride smoke plume in 25 cm s-1 wind. (Aii) Point-source plume, 2.8 cm high at the source, spreads to maximum of 22.4 cm and decreases to 8.4 cm at the downwind end. (Bii) Ribbon plume, 2.2 cm high at the source, spreads to maximum of 22.2 cm and decreases to 10.1 cm at the downwind end. (Cii) Wide plume, 5.6 cm high at the source, spreads to maximum of 38.4 cm and decreases to 22.4 cm high at the downwind end. (Dii) Cylinder plume, 56 cm high at the source (maximum), spreads to 54.3 cm at the downwind end.

View larger version (29K): [in a new window]   Fig. 2. Walking orientation of P. americana males in (A) No wind + no pheromone, (B) wind + no pheromone and (C) wind + point-source pheromone. Arrowheads indicate the orientation of the cockroach at the end of the track in laboratory wind tunnel. The circle represents the release cage. Vanishing direction (angle from release point to point where the cockroach leaves the field of view of the camera) is displayed in the angular histogram to the left with the mean resultant length (r) associated with the mean direction (). Day 1, 17/4/03; Day 2, 22/4/03; Day 3, 22/4/03; Day 4, 7/5/03.

View larger version (35K): [in a new window]   Fig. 3. Examples of P. americana males tracking female pheromone upwind (direction right to left) in a wind tunnel illustrated with the time-averaged plume boundaries of titanium tetrachloride smoke visualization of the plumes as they track in 25 cm s-1 wind. Each circle represents the body position every 0.083 s. Details of the time-averaged plume envelopes as per Fig. 1.

View larger version (29K): [in a new window]   Fig. 4. Time-averaged plume boundaries of point-source and wide plumes with the track of the cockroach head (solid line) and the tips of the left and right antennae (broken lines). (A) Upwind track of a P. americana male in a point-source plume. Shallow v-shaped lines indicate the position of the left and right antennae and the head position at important points along the track. The timing of these points, with respect to the zero time at which the male entered the field of view of the camera, is indicated in association with each antennal position. The time signatures represent: 0.56 s, contact of the left antenna with the time-averaged plume boundaries; 0.73 s, loss of contact between plume and the left antenna; 1.06 s, initiation of left turn; 1.19 s, re-contact between the left antenna and the time-averaged plume. (B) Upwind track of a P. americana male in a wide plume. In each example the upper box represents the overhead view of the track. An exploded view of the indicated short section of the track shows the cockroach head (solid line) and tips of the left and right antennae (broken lines). Below is the exploded view from the side. Cockroaches are traveling upwind from right to left. Details as per Figs 1 and 3.

View larger version (13K): [in a new window]   Fig. 5. Body pitch angle of P. americana walking in (A) no wind + no pheromone, (B) wind + no pheromone and (C) wind + pheromone. The black line and light gray shaded area indicate the mean ± S.D. The dark gray shaded area represents the maximum and minimum pitch angles reached out of the entire experimental population.