A Guide for Using Flight Simulators to Study the Sensory Basis of Long-Distance Migration in Insects.

David Dreyer,Barrie Frost,Eric Warrant,Adrien Lefèvre,Henrik Mouritsen,Myles Menz

doi:10.3389/fnbeh.2021.678936

Abstract

Studying the routes flown by long-distance migratory insects comes with the obvious challenge that the animal’s body size and weight is comparably low. This makes it difficult to attach relatively heavy transmitters to these insects in order to monitor their migratory routes (as has been done for instance in several species of migratory birds. However, the rather delicate anatomy of insects can be advantageous for testing their capacity to orient with respect to putative compass cues during indoor experiments under controlled conditions. Almost 20 years ago, Barrie Frost and Henrik Mouritsen developed a flight simulator which enabled them to monitor the heading directions of tethered migratory Monarch butterflies, both indoors and outdoors. The design described in the original paper has been used in many follow-up studies to describe the orientation capacities of mainly diurnal lepidopteran species. Here we present a modification of this flight simulator design that enables studies of nocturnal long-distance migration in moths while allowing controlled magnetic, visual and mechanosensory stimulation. This modified flight simulator has so far been successfully used to study the sensory basis of migration in two European and one Australian migratory noctuid species.

Highlights

Like the North American Monarch butterfly, many species of moths have been identified as long-distance migrants (Williams, 1958)
The Mouritsen-Frost flight simulator was initially designed to record the orientation choices of diurnal insects during their migration (Mouritsen and Frost, 2002). Relative to their “natural orientation behavior,” a subpopulation of tethered flying insects can be tested under conditions in which the spatial orientation of a putative compass cue is altered, with the goal of determining whether the insects compensate for this alteration
Apart from this obvious application, one can use the flight simulator to investigate the influence of external “disturbance factors,” such as an artificial light stimulus of certain intensity, polarization, and/or wavelength, on the flight performance of insects

Summary

INTRODUCTION

Like the North American Monarch butterfly, many species of moths have been identified as long-distance migrants (Williams, 1958). To test the effects of an Earth-strength magnetic field on the flight behavior of moths, the behavioral arena can be placed within a double-wrapped (Kirschvink, 1992; Mouritsen, 1998; Schwarze et al, 2016), computerized 3D-Helmholtz coil system consisting of three pairs of orthogonally mounted coils: the X-, Y-, and Z-coils (Figure 5C) This computer-controlled Helmholtz coil system enables us to send minute currents through the paired X-, Y-, and Z- coils which result in changes in the magnitude of the respective component vectors (measured in nano Tesla, nT) and in changes in the resulting magnetic field vector. In addition to accurately producing and adjusting natural geomagnetic fields within the flight arena, the coils are able to create a "magnetic vacuum" (i.e., a nulled, or zeroed field; Mouritsen, 1998) around the moth (see Figure 5B) A Meda FVM-400 magnetometer, the probe of which is placed at the position of the moth, is used to ensure that the magnetic field is correctly set with the appropriate field parameters for the experiment at hand

EXPERIMENTAL PROCEDURES

Findings

CONCLUSION