ABSTRACT
Anyone who has handled the blood-sucking bugs, Triatoma or Rhodnius, must have observed that they are often attracted to the sides of their jars at places where these have been warmed by recent handling, and that they will probe such spots vigorously with the proboscis. This behaviour suggests that they are attracted to their host mainly by warmth1—a belief which is supported by the recent observations of Rivnay (1932) on the bed bug (Cimex) and of Hase (1932) on various Triatomidae. Further, the movements of the antennae, which precede the location of the host, suggest that these carry the sense organs concerned ; and we were led to undertake the present work because it seemed possible that Rhodnius might prove a favourable subject in which to study both the function of the antennae, and the mechanism by which they secure the orientation of the insect in relation to its host. More particularly we hoped to define this mechanism in terms of the current theories of orientation (Loeb, 1918; Kühn, 1919; Fraenkel, 1931).
At least at short range, that is, just at the time of feeding. It is possible that they find themselves near their host merely by chance (as suggested by Kemper, 1929, 1932, in Cimex), or that they are attracted from a distance by vibrations or other stimuli.
The insects were normally fed on the rabbit, but they will feed on other warm-blooded animals and man with equal readiness.
Kühn’s mnemotaxii is here excluded.
The terrible confusion that centres around the term “tropism” is discussed by Mast (1915, 1923).
It may be noted in passing that Mast (1923) and Clark (1931) have shown that both these reactions may be explained upon a reflex theory without invoking effects on muscle tone.
Thia is well illustrated by the following observation. Normally, if the antenna of Rhodnius is touched by a cold object it is quickly withdrawn and the insect retreats. But if touched by such an object while the insect is advancing towards a source of stimulus, the proboscis is at once extended.
As Brecher remarks, “P. americana Iâuft ihrer Antenne nach.”
