Further observations on correcting behaviour in boxelder bugs

Abstract

1. 1. After making a forced turn on a causeway, boxelder bugs make a turn on a platform in a direction opposite to the forced turn. The angle turned on the platform increases abruptly or in sigmoid fashion as the start to forced turn distance increases. Blinded bugs show a similar effect, but the angle is reduced and the increase is not sigmoid or abrupt. 2. 2. After running for most of the distance between start and forced turn, bugs can be delayed for 40 seconds or more without effect on mean angle turned on the platform. 3. 3. At a certain critical forced turn angle, between 60 ° and 75 °, the frequency of turns at a choice point offering either a turn opposite to the forced turn or a straight path markedly increases (with the start to forced turn and forced turn to choice point distances kept constant). 4. 4. If bugs were made to circle on a causeway, they would turn opposite to the direction of circling upon arrival at a platform. The amount of turn increased as distance run increased or as the radius of the circling arc decreased. Two important factors thus seem to be distance travelled and rate of change of direction. 5. 5. Blinding reduces the degree of opposite turning made at a choice point after making an abrupt forced turn and the opposite direction turned on a platform after traversing a circling arc. Opposite turning is, however, still present to some extent. It is the lower halves of the eyes which are important. 6. 6. Explanations of the above behaviour based on “centrifugal swing” and “reactive inhibition” are rejected. 7. 7. Events occurring at the forced turn probably interact with an excitatory state built up between the start and the forced turn to cause opposite turning at a choice point. Whatever the excitation state, it builds up in sigmoid or abrupt fashion and endures for a period of at least 40 seconds. 8. 8. Vision certainly, and proprioception probably, are important factors in the performance of the above behaviour.