CHEMORECEPTION AND THE BEHAVIOR OF INSECTS
151
port, 1955), refreshingly new studies of the behavior of honeybees
(Butler, 1954; Ribbands, 1953; von Frisch, 1954), and a reexamination of
the whole question of food-plant choice by phytophagous insects
(Dethier, 1947a, 1953b, 1954a).
No more forceful example of this progress can be found than that of
host-finding and recognition by parasitoid insects. Following a description of host-parasite interactions, the present discussion will turn to two
examples of orientation which have been selected as representative of the
advances of recent years, namely, chemical trail-following and orientation to airborne odors. Finally, there will be presented two examples of
behavior which are consequent upon a goal having been achieved,
namely, courting and mating in Orosophila and in cockroaches.
II. HOST-FINDING AND RECOGNITION BY
PARASITIOD INSECTS
The earliest modern major attempt to understand the means whereby
an insect parasitoid locates and recognizes its host is represented by the
discussion of Thompson and Parker (1927) a propos of host selection
by the chalcid wasp Melittobia acasta Walk, and the tachinid fly Compsilura concinnata Meig. These authors concluded that ". . . the problem
of host relations is not one which is fundamentally amenable to scientific
treatment." What they really meant by this pessimistic statement was
that the choice of hosts is not a phenomenon which is referable to any
constant definite efficient cause exterior to the organism, i.e., that the
behavior of the parasite is not strictly determined if considered simply
in relation to the physico-chemical properties of the host. In their
opinion the problem is a psychological one which can be understood
only by comparison with similar phenomena in man, as, for example, the
choice of food. This opinion was undoubtedly a reaction against the
excessively mechanistic Loebian approach to behavior. The central
theme of the opinion is fundamentally correct, namely, that the behavior
of the parasite is not strictly determined if considered solely in relation
to stimuli originating in the external environment, namely, the host.
This is just the problem which Tinbergen (1951) attempted to elucidate
but which depends so much for its solution upon some concept of the
effect on behavior of external physico-chemical changes. As he stated:
"Instinctive behaviour is dependent upon external and internal
causal factors. The external factors, or sensory stimuli, are of a
much simpler nature than our knowledge of the potential capacities
of the sense organs would make us expect. Yet they are not so
simple as the word 'stimulus' would suggest, for the 'sign stimuli'
have gestalt character, that is to say, they release configurational
151
port, 1955), refreshingly new studies of the behavior of honeybees
(Butler, 1954; Ribbands, 1953; von Frisch, 1954), and a reexamination of
the whole question of food-plant choice by phytophagous insects
(Dethier, 1947a, 1953b, 1954a).
No more forceful example of this progress can be found than that of
host-finding and recognition by parasitoid insects. Following a description of host-parasite interactions, the present discussion will turn to two
examples of orientation which have been selected as representative of the
advances of recent years, namely, chemical trail-following and orientation to airborne odors. Finally, there will be presented two examples of
behavior which are consequent upon a goal having been achieved,
namely, courting and mating in Orosophila and in cockroaches.
II. HOST-FINDING AND RECOGNITION BY
PARASITIOD INSECTS
The earliest modern major attempt to understand the means whereby
an insect parasitoid locates and recognizes its host is represented by the
discussion of Thompson and Parker (1927) a propos of host selection
by the chalcid wasp Melittobia acasta Walk, and the tachinid fly Compsilura concinnata Meig. These authors concluded that ". . . the problem
of host relations is not one which is fundamentally amenable to scientific
treatment." What they really meant by this pessimistic statement was
that the choice of hosts is not a phenomenon which is referable to any
constant definite efficient cause exterior to the organism, i.e., that the
behavior of the parasite is not strictly determined if considered simply
in relation to the physico-chemical properties of the host. In their
opinion the problem is a psychological one which can be understood
only by comparison with similar phenomena in man, as, for example, the
choice of food. This opinion was undoubtedly a reaction against the
excessively mechanistic Loebian approach to behavior. The central
theme of the opinion is fundamentally correct, namely, that the behavior
of the parasite is not strictly determined if considered solely in relation
to stimuli originating in the external environment, namely, the host.
This is just the problem which Tinbergen (1951) attempted to elucidate
but which depends so much for its solution upon some concept of the
effect on behavior of external physico-chemical changes. As he stated:
"Instinctive behaviour is dependent upon external and internal
causal factors. The external factors, or sensory stimuli, are of a
much simpler nature than our knowledge of the potential capacities
of the sense organs would make us expect. Yet they are not so
simple as the word 'stimulus' would suggest, for the 'sign stimuli'
have gestalt character, that is to say, they release configurational