Olfactory Stimulation of Blowflies by Homologous Alcohols

Abstract

The response of the blowfly Phormia regina to stimulation by alcohols in the vapor phase has been investigated by means of an olfactometer which permitted quantitative control of stimulus concentration. The median rejection threshold was selected as a criterion of response. As was true in the case of contact chemoreception, the distribution of thresholds in the fly population is normal with respect to the logarithm of concentration. In terms of molar concentration the alcohols are rejected at logarithmically decreasing concentration as chain length is increased. Beyond decanol there is no further stimulation. When thresholds are expressed as pressures and plotted against saturated vapor pressures on logarithmic coordinates, the data fit a line the slope of which is not significantly different from 1; i.e., the thresholds vary directly with vapor pressure. Individual threshold values, however, deviate significantly from this line. and the deviation must be ascribed to other factors which have not as yet been identified. When thresholds are expressed as activities, all alcohols are equally stimulating. It appears that the limiting process of olfaction, at least in so far as the normal alcohols are concerned, may involve an equilibrium process. Conformity to this concept is most exact for intermediate members of the series.

Thresholds for odor and nasal pungency

“…Insert Figure 6 about here The present results on the relative olfactory efficiency of the homologous alcohols in terms of thermodynamic activity agree well with previous human data (44) and with studies of behavioral olfactory responses in blowflies (27), electrophysiological olfactory responses in frogs (45) and behavioral olfactory responses in rats (43). Our data indicating a constant pungency efficiency in terms of thermodynamic activity for these same stimuli as perceived by human anosmics differ from electrophysiological activity thresholds obtained from the ethmoid branch of the rat trigeminal nerve which showed a monotonic decrease of activity with carbon chain length (53).…”

Summation and Inhibition Following Contralateral Stimulation of the Tarsal Chemoreceptors of the Blowfly

“…The beetle Laccophilus is stimulated to greater swimming activity by alcohols (Hodgson, 1951). Phormia is stimulated via the antennae to greater flying activity by alcohol vapors (Dethier and Yost, 1952), and Drosophila (Reed, 1938) is attracted by low concentrations of short-chain aliphatic alcohols. On the other hand, it is also known that short exposure to high concentrations or prolonged exposure to lower concentrations of alcohols will result in narcosis.…”

Sensilla on the antennal funiculus of the blow fly, Protophormia terraenovae (Diptera: Calliphoridae)

“…antennal funiculus of Phormia regina (Dethier, 1952(Dethier, , 1954(Dethier, , 1961(Dethier, , 1971(Dethier, , 1976Dethier et al, , 1963Dethier and Yost, 1952;Lieberman, 1926) and Calliphora vicina (Kaib, 1974). In more recent investigations, the external organization of antennal sensilla has been described and an olfactory function has been suggested for most sensillar structures on the antennal funiculus of Cochliomyia hominivorax (Fernandes et al, 2004), Chrysomya megacephala, Chrysomya rufifacies, Chrysomya nigripes and Lucilia cuprina (Sukontason et al, 2004).…”