Horizontal and vertical movements of first-instar western corn rootworms, Diabrotica virgifera virgifera LeConte, were studied in a 30-cm soil chamber filled with silt loam, sandy loam, or sand at various bulk densities. Larvae were released in one end of the chamber with a carbon dioxide (CO2) source present in the far end of the chamber in half of the uncompacted and all of the compacted tests. Horizontal larval distributions were determined after 6 h in uncompacted and 20 h in compacted soils. In all uncompacted soils, larvae became evenly distributed in the absence of CO2 within 6 h; in the presence of CO2, >66% of the larvae moved at least 25 cm toward the CO2 source. Increases in soil bulk density inhibited larval movement to varying degrees. Vertical distributions were measured after 20 h in uncompacted soil in the absence of the CO2 source. Significantly more upward rather than downward movement occurred.
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Strnad et al. (1987) studied this question.