Random movement pattern of fed and unfed adult Colorado potato beetles in bare-ground habitat.

摘要

Although the successful management of the Colorado potato beetle Leptinotarsa decemlineata (Say) depends on the prevention of its dispersal, its walking pattern in the landscape remains poorly understood. In the present study, post-diapause, early summer, late summer and colony adult beetles, both fed and unfed before release, were tracked with a harmonic radar to establish their walking movement pattern in a bare-ground field. The random walk model successfully described the dispersal of all beetle types, whether fed or unfed. The diverse life history of this species was manifested by an increased distance travelled and deviations of individual paths from the random model. Starved post-diapause beetles travelled furthest and individual paths deviating from random were both local and directed, probably aiming to maximize opportunities for host colonization. Starved early summer beetles also travelled further than fed beetles but relied more on random movement to disperse in the habitat. Starving had little impact on the distance travelled or the path deviations of late summer beetles that are searching for overwintering site rather than hosts. The increased displacement of starving beetles over fed beetles corresponded with an increased walking step and index of straightness. The impact of starvation on travel distance was greater than expected from laboratory tests. In conclusion, the results obtained in the present study suggest a random walking pattern to search arable land until host volatile or visual impulses trigger a more directed walk or flight.