170
V. G. DETHIER
operated specimens, and that, even were a tropotaxis demonstrable in
the operated insects, it would not necessarily imply that this was the
method of orientation in intact individuals. Flügge was of the opinion
that, since tropotaxis is the principal means of orientation by
Drosophih
in high odor concentrations, the relatively poor performance of flies with
one antenna results from the fact that orientation by means of one receptor organ is poorly developed. Sengün (1954), in his experiments
with olfactory orientation of Bombyx mori, also observed that moths with
one antenna experienced greater difficulty and required a longer time
to locate the odor source. Most workers feel that in high odor concentrations, i.e., near the source, the paths of the orienting insects are relatively
straight. Sengün believed that the failure of the path to be absolutely
straight, as it would be in the case of an animal orienting tropotactically
to light, results from the fact that the odor path is not uniform like light
but is so tortuous that a classical tropotactic path is distorted. But the
experiments of Schwinck with the same insect gave no evidence of tropotaxis either in terms of the path pursued or in the behavior of moths
lacking one antenna.
Most of the aforementioned workers (Murr, Warnke, Flügge, Härtung,
and Sengün) believed that the mechanism of orientation at low odor
concentrations, i.e., at some distance from the odor source, differs from
that close to the source. As already mentioned, they thought that the
latter is tropotaxis. The former they called a phobotaxis, and those who
did not believe that tropotaxis is involved at all described the entire
process of orientation in terms of phobotaxis. By phobotaxis they meant
a type of behavior which falls into the Fraenkel and Gunn (1940) classification of orientation mechanisms under the headings klinokinesis
and/or klinotaxis (see also Koehler, 1950). Schwinck (1954) proposed a
new classification to cover these situations. For trial and error reactions
based upon successive perceptions of bilateral sense organs or unilateral
sense organs moved from side to side she proposed the term strophotaxis
with two subdivisions, makrostrophotaxis as a substitute for klinokinesis
(— phobotaxis) and mikrostrophotaxis as a substitute for klinotaxis
(— pseudotropotaxis). No changes were proposed for the classification
of other types of orientation reactions. In any case it seems clear that
insects orienting to an odor-bearing stream, especially at some distance
from the source, pursue a somewhat erratic path, turn away from the
side of no stimulation every time they come to the periphery of the
stream, and in the absence of stimulation resort to a tortuous "searching"
type of behavior until they again encounter the odor-bearing current.
Most workers have agreed that the olfactory stimulation serves principally to initiate a positive anemotaxis (i.e., response to an air stream),
V. G. DETHIER
operated specimens, and that, even were a tropotaxis demonstrable in
the operated insects, it would not necessarily imply that this was the
method of orientation in intact individuals. Flügge was of the opinion
that, since tropotaxis is the principal means of orientation by
Drosophih
in high odor concentrations, the relatively poor performance of flies with
one antenna results from the fact that orientation by means of one receptor organ is poorly developed. Sengün (1954), in his experiments
with olfactory orientation of Bombyx mori, also observed that moths with
one antenna experienced greater difficulty and required a longer time
to locate the odor source. Most workers feel that in high odor concentrations, i.e., near the source, the paths of the orienting insects are relatively
straight. Sengün believed that the failure of the path to be absolutely
straight, as it would be in the case of an animal orienting tropotactically
to light, results from the fact that the odor path is not uniform like light
but is so tortuous that a classical tropotactic path is distorted. But the
experiments of Schwinck with the same insect gave no evidence of tropotaxis either in terms of the path pursued or in the behavior of moths
lacking one antenna.
Most of the aforementioned workers (Murr, Warnke, Flügge, Härtung,
and Sengün) believed that the mechanism of orientation at low odor
concentrations, i.e., at some distance from the odor source, differs from
that close to the source. As already mentioned, they thought that the
latter is tropotaxis. The former they called a phobotaxis, and those who
did not believe that tropotaxis is involved at all described the entire
process of orientation in terms of phobotaxis. By phobotaxis they meant
a type of behavior which falls into the Fraenkel and Gunn (1940) classification of orientation mechanisms under the headings klinokinesis
and/or klinotaxis (see also Koehler, 1950). Schwinck (1954) proposed a
new classification to cover these situations. For trial and error reactions
based upon successive perceptions of bilateral sense organs or unilateral
sense organs moved from side to side she proposed the term strophotaxis
with two subdivisions, makrostrophotaxis as a substitute for klinokinesis
(— phobotaxis) and mikrostrophotaxis as a substitute for klinotaxis
(— pseudotropotaxis). No changes were proposed for the classification
of other types of orientation reactions. In any case it seems clear that
insects orienting to an odor-bearing stream, especially at some distance
from the source, pursue a somewhat erratic path, turn away from the
side of no stimulation every time they come to the periphery of the
stream, and in the absence of stimulation resort to a tortuous "searching"
type of behavior until they again encounter the odor-bearing current.
Most workers have agreed that the olfactory stimulation serves principally to initiate a positive anemotaxis (i.e., response to an air stream),