Direct chemo-orientation

The last method for inferring instantaneous comparison and direct chemo-orientation is through statistical analysis of discrete turn angles relative to the chemical gradient. For example, the male cockroach, P. americana, turns more directly toward a sex pheromone source (in still air) within 35 cm of the source then when it is more distant from the source. Whereas the turn accuracy is the same for unilaterally antennectomized males as for intact males between 35 and 70 cm of the source, turns within 35 cm are more accurate in intact than one-antenna males (Bell and Tobin, 1981). Discrete turns up the concentration... 

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