THE RELATION BETWEEN OLFACTORY RESPONSE AND RECEPTOR POPULATION IN THE BLOWFLY

Abstract

Measurements were made of thresholds of rejection of 2 concns. of pentanol vapor by normal Phormia regina and those from which various head appendages have been removed. The concns. selected were 5.0 x 10-6 [image] pentanol, to which 90% of the population normally responds, and 1.6 x 10-6[image], to which approx. 25% of the population normally responds. The results show that the response elicited depends upon stimulation of specialized receptors present on the antennae and palpi and hence cannot be attributed to the action of a common chemical sense. Repellents in the gas phase undoubtedly act as olfactory stimuli. Different receptor fields function at different levels of sensitivity. The antennae are the most sensitive and the various mouth-parts less so. There is also a relation between threshold and the number of receptors functioning. Insects possessing both antennae respond to lower concns. of odor than those bearing only one. This indicates that the 2 sides of the body are acting in concert. Whether it represents true neural contralateral summation or is based upon statistical bias cannot yet be decided. In either case, from the point of view of coordinated behavior it illustrates the manner in which bilaterally placed receptor fields may operate as a unit.