CHEMORECEPTION AND THE BEHAVIOR OF INSECTS
175
of the antennae. For example, fecundation in D. pseudoobscura
in the
absence of antennae was reduced from 95% to 50% and in D. persimilis
from 95% to 8.4%. In darkness it was reduced to 26.2% and 0.8%, respectively. These results demonstrate the importance of stimulation received
through the antennae, and also the importance of summing of heterogeneous stimuli.
If the female accepts the posturing male, as indicated by a slight
spreading of the vaginal plates, the male of many species will now more
or less briefly insert his proboscis. In species in which this is the rule
the male will not mount until he has performed this action. There is
a very great likelihood that the sense organs stimulated are the contact
chemoreceptive hairs on the labellum. In the subgenus Sophophora
the
period of licking is extremely short or absent. Thus, in the experiments
which Streisinger performed on etherized females, the males of D. melanogaster, a species which licks only briefly, either cannot discriminate
species by this action or are so promiscuous as to ignore the difference.
It would be interesting to ascertain whether a male of a species where
licking is a means of species discrimination could still discriminate after
the labellum had been removed. The sensory physiology of the labellum
is well known (Dethier, 1955), and an experiment of this nature would
further our knowledge of the process.
The process of courting and copulation as a whole evidently releases
stimuli which remain in the vicinity and serve as stimuli to other pairs
of flies nearby. Sturtevant (1915) found, for example, that pairs of D.
melanogaster
could be induced to copulate more readily if placed in a
vial which had previously housed a copulating pair; but the nature of the
stimulus, whether it is odorous or perceived by the tarsi on contact, is
unknown.
VI. MATING BEHAVIOR: COCKROACHES
Intricate refinements of courtship are by no means the assets solely of
insects like Drosophila which have climbed high on the evolutionary
scale. Even the lowly and primitive cockroach indulges in a courtship
worthy of the serious attention of biologists. The oft-quoted phrase of
Snodgrass (1937) is still pertinent: "Considering how intimate some of
the cockroaches are with us, it is disconcerting to find how little we know
of the private lives of cockroaches." We do know that cockroaches
possess characteristic odors elaborated at least in part in a variety of
glands which are anal, tergal, or sternal.
The German cockroach (Blatella germanica)
engages in an elaborate
courtship which has been described on numerous occasions. Roth and
Willis (1952a) have recently reinvestigated the sexual behavior of this
175
of the antennae. For example, fecundation in D. pseudoobscura
in the
absence of antennae was reduced from 95% to 50% and in D. persimilis
from 95% to 8.4%. In darkness it was reduced to 26.2% and 0.8%, respectively. These results demonstrate the importance of stimulation received
through the antennae, and also the importance of summing of heterogeneous stimuli.
If the female accepts the posturing male, as indicated by a slight
spreading of the vaginal plates, the male of many species will now more
or less briefly insert his proboscis. In species in which this is the rule
the male will not mount until he has performed this action. There is
a very great likelihood that the sense organs stimulated are the contact
chemoreceptive hairs on the labellum. In the subgenus Sophophora
the
period of licking is extremely short or absent. Thus, in the experiments
which Streisinger performed on etherized females, the males of D. melanogaster, a species which licks only briefly, either cannot discriminate
species by this action or are so promiscuous as to ignore the difference.
It would be interesting to ascertain whether a male of a species where
licking is a means of species discrimination could still discriminate after
the labellum had been removed. The sensory physiology of the labellum
is well known (Dethier, 1955), and an experiment of this nature would
further our knowledge of the process.
The process of courting and copulation as a whole evidently releases
stimuli which remain in the vicinity and serve as stimuli to other pairs
of flies nearby. Sturtevant (1915) found, for example, that pairs of D.
melanogaster
could be induced to copulate more readily if placed in a
vial which had previously housed a copulating pair; but the nature of the
stimulus, whether it is odorous or perceived by the tarsi on contact, is
unknown.
VI. MATING BEHAVIOR: COCKROACHES
Intricate refinements of courtship are by no means the assets solely of
insects like Drosophila which have climbed high on the evolutionary
scale. Even the lowly and primitive cockroach indulges in a courtship
worthy of the serious attention of biologists. The oft-quoted phrase of
Snodgrass (1937) is still pertinent: "Considering how intimate some of
the cockroaches are with us, it is disconcerting to find how little we know
of the private lives of cockroaches." We do know that cockroaches
possess characteristic odors elaborated at least in part in a variety of
glands which are anal, tergal, or sternal.
The German cockroach (Blatella germanica)
engages in an elaborate
courtship which has been described on numerous occasions. Roth and
Willis (1952a) have recently reinvestigated the sexual behavior of this