Recruitment by Flight and Walking in a One-Generation Colorado Potato Beetle (Coleoptera: Chrysomelidae) Environment

Abstract

Adult Colorado potato beetle, Leptinotarsa decemlineata (Say), recruitment on potato plots by flight or by walking occurred throughout the 1991–1993 crop seasons. Most recruitment occurred by walking. Yearly recruitment by flight ranged from 9.5 to 49.4%. It is suggested that the proportion of recruitment occurring by flight is determined largely by environmental factors such as air temperature and solar radiation. The presence of well-developed flight muscles is necessary for flight but was not a limiting factor until late August and even then only for part of the population. The proportion of beetles with developed thoracic muscle masses, developed ovaries, high abdominal fat content levels, and sperm in the spermatheca did not significantly differ between beetle populations recruited by flight or by walking but did differ between the overwintered and summer groups. A significant proportion of beetles that colonized potato plots by flight emigrated from the plots by walking on the same day throughout each crop season. This suggests that most beetles use both flight and walking to disperse throughout the day depending on the “task” and environmental conditions. A large proportion of summer adults in prediapause condition retain the ability to disperse by flight when conditions are appropriate such as in 1991 in this study. Results confirm that potato beetle recruits counted on plants or collected in ground traps have an overall 0.41 sex ratio but those collected in flight traps have a 0.52 sex ratio. There was no indication that the sex ratio plays a significant role in determining the relative contribution of walking and flight to recruitment. A diapausing switch in early August responsible for prediapausing conditions in the summer population of beetles occurs in New Brunswick. The switch did not entirely prevent dispersal to the crop by flight as reported elsewhere for more southern locations.