CHEMORECEPTION AND THE BEHAVIOR OF INSECTS
167
i.e., 14.2 χ 10
6 g. per individual. A male can be activated by as little
as 1 X 10'
8 g. Assuming ideal conditions, i.e., continuous production by
the females, complete evaporation, diffusion in still air, and a zone of
action resembling a cone, then at a distance of ten kilometers there
would be one molecule in every cubic centimeter of air. Teuber believes
that the high molecular weight of the attractant precludes a low vapor
pressure and that the drop in concentration around the diffusing female
does not supply a sufficient concentration gradient to permit orientation.
This conclusion is without a doubt correct. To solve this dilemma however, Barth, Teudt, and others proposed an alternative hypothesis to
replace the usually accepted one that odor molecules act by impinging
on the olfactory receptors. Briefly, the idea is that the odor molecule is
unstable in the vapor phase and rapidly decomposes. [According to
Schwinck (1954), however, the sex attractant of Bombyx mori does not
decompose as readily as is claimed.] By virtue of valency electron vibrations it is an energy-sender; resonance is set up in the air and transmitted
over the effective distance independently of the odor particles to increase
the olfactory effect. Electron vibrations within the sensory apparatus
are then increased or modified by resonance.
Various articles in the popular press report work by amateurs which
purports to prove that female moths emanate energy in the form of
infrared, in particular, wavelengths of 8-40 π\μ., which may be picked up
by the antennae of males. All of these writings are highly speculative,
and experiments, when done, have not been sufficiently well controlled
to be of value. They do not satisfactorily account for the attraction exercised by extracts of female scent substance, and they place rather
severe demands on the law of conservation of energy.
It is a curious and rather discouraging reflection that those who investigate desultorily prefer to solve apparent dilemmas by advancing
radical hypotheses rather than by assuming the less ostentatious drudgery of critically reexamining data which have led to the dilemma and,
where necessary, by undertaking to perform missing, crucial experiments! A careful analysis of the investigations of distance orientation by
insects to odor sources as reported during the last twenty-five years
provides an adequate explanation of assembling and other responses to
odor, an explanation which does not require the intervention of phenomena whose role has not yet been demonstrated experimentally. Much
of this work, especially the recent experiments of Schwinck (1954) with
Bombyx mori, invalidates many of the premises upon which radiation
hypotheses depend and shows that orientation at a fair distance is possible even though there may not be a sufficient number of molecules to
allow for the establishment of a concentration gradient.
167
i.e., 14.2 χ 10
6 g. per individual. A male can be activated by as little
as 1 X 10'
8 g. Assuming ideal conditions, i.e., continuous production by
the females, complete evaporation, diffusion in still air, and a zone of
action resembling a cone, then at a distance of ten kilometers there
would be one molecule in every cubic centimeter of air. Teuber believes
that the high molecular weight of the attractant precludes a low vapor
pressure and that the drop in concentration around the diffusing female
does not supply a sufficient concentration gradient to permit orientation.
This conclusion is without a doubt correct. To solve this dilemma however, Barth, Teudt, and others proposed an alternative hypothesis to
replace the usually accepted one that odor molecules act by impinging
on the olfactory receptors. Briefly, the idea is that the odor molecule is
unstable in the vapor phase and rapidly decomposes. [According to
Schwinck (1954), however, the sex attractant of Bombyx mori does not
decompose as readily as is claimed.] By virtue of valency electron vibrations it is an energy-sender; resonance is set up in the air and transmitted
over the effective distance independently of the odor particles to increase
the olfactory effect. Electron vibrations within the sensory apparatus
are then increased or modified by resonance.
Various articles in the popular press report work by amateurs which
purports to prove that female moths emanate energy in the form of
infrared, in particular, wavelengths of 8-40 π\μ., which may be picked up
by the antennae of males. All of these writings are highly speculative,
and experiments, when done, have not been sufficiently well controlled
to be of value. They do not satisfactorily account for the attraction exercised by extracts of female scent substance, and they place rather
severe demands on the law of conservation of energy.
It is a curious and rather discouraging reflection that those who investigate desultorily prefer to solve apparent dilemmas by advancing
radical hypotheses rather than by assuming the less ostentatious drudgery of critically reexamining data which have led to the dilemma and,
where necessary, by undertaking to perform missing, crucial experiments! A careful analysis of the investigations of distance orientation by
insects to odor sources as reported during the last twenty-five years
provides an adequate explanation of assembling and other responses to
odor, an explanation which does not require the intervention of phenomena whose role has not yet been demonstrated experimentally. Much
of this work, especially the recent experiments of Schwinck (1954) with
Bombyx mori, invalidates many of the premises upon which radiation
hypotheses depend and shows that orientation at a fair distance is possible even though there may not be a sufficient number of molecules to
allow for the establishment of a concentration gradient.