Adult Density and the Rate of Colorado Potato Beetle (Coleoptera: Chrysomelidae) Flight Take-Off

Abstract

The suggestion in the literature that dispersal of the Colorado potato beetle, Leptinotarsa decemlineata (Say), by flight is stimulated by crowding was tested in three flight chamber experiments. In the first experiment the rate of take-off in flight chambers averaged 35.0% (SE ± 5.64) over a 3-h period. The rate of flight take-off was independent of insect density (2–128 beetles per release) or age (7–18 after emergence). For the second experiment the cumulative incidence of flight take-off rates during a 3-h period was similar for all insect densities. The mean percentage of beetles that flew was greatest in the first 30 min, was low during the following 30 min and minimal thereafter. At the highest density tested, i.e., 128 beetles per release, the take-off rate was initially lower; however, it resulted in the same 3-h cumulative rate as for other densities. The data show that interactions between crowded individual adult potato beetles do not promote flight take-off and might occasionally lower it. The third experiment included a 1-h acclimatization to the experimental setup but had no effect on the mean rate of flight take-off or its pattern over the subsequent 3-h period. These results provide evidence that the massive dispersal of adult beetles occasionally observed in potato fields is not the result of crowding as suggested by some, but is probably caused by the poor quality or near absence of the host plants (food source) in the fields with abundant beetles.