Research Institute for Plant Protection IPO-DLO, Wageningen, The Netherlands
In olfactometers the analysis of insect behaviour in response to semiochemicals is difficult and, generally, does not reveal the details of the walking tracks underlying the insect's decisions. Moreover, the dimensions of such instruments strongly affect the tracks as insects are thigmotactically guided by its walls. The disadvantages are overcome by the complete compensation of insect movements on a servosphere. Here I describe the setup of a locomotion compensator, which has been originally designed by E. Kramer and P. Heinecke and was introduced in The Netherlands as early as 1981.
The instrument operates as follows: a piece of reflective material is glued on the back of an insect. The insect is placed on top of a 50-cm sphere, and observed by a detector. The detector projects a beam of light onto the insect, which is reflected by means of the 'mirror' on the insect's back; thus the position of the animal is detected. As soon as the insect starts walking its positional change is seen by the detector, which initiates that two motors rotate the sphere in the opposite direction with the same speed as the insect is walking. As a result, the insect stays on top of the sphere while walking. The "infinite space" of a locomotion compensator permits fully unconstrained movement and thus avoids the behavioral artefacts inherent to experimental setups based on an enclosure (arena, petri dish, olfactometer, etc.). The rotations of the sphere are detected by two pulse generators in contact with the sphere and speed and direction are calculated every second. A number of parameters were developed which precisely quantify the actual track.
The instrument has been used successfully for measuring the orientation behavior of a large variety of insects, including aphids, beetles, bugs, cockroaches, crickets, honeybees and parasitoid wasps.
We are currently investigating the feasibility of commercialization of this instrument. Besides that we are assessing its applicability to the study of locomotory orientation in other animals, such as rodents. Readers who are potentially interested are invited to contact the author.