Experimental analysis of flight activity of three Dalbulus leafhoppers (Homoptera: Auchenorrhyncha) in relation to migration.
The flight periodicities of 3 species of Dalbulus were monitored in a controlled-environment chamber using segregating suction traps. To assess their effect on flight activity, photoperiod and host plant age were experimentally manipulated to mimic conditions at different seasons in central Mexico. All 3 species flew during the crepuscular periods. Comparisons of the flight periodicity of the 3 species suggested that the maize specialists, D. maidis and D. elimatus, are more likely than D. gelbus (a gamagrass (Tripsacum spp.) and maize feeder), to fly from mature maize plants at the end of summer. The second flight of the day of D. elimatus under simulated autumn conditions occurred in the middle of the afternoon when atmospheric instability is greatest and flight would result in emigration. Unexpectedly, the widespread pest species D. maidis displayed a lesser tendency to leave old maize in autumn than the high elevation endemic, D. elimatus. However, the flight behaviour of D. maidis is consistent with winter (short photoperiod) migratory flight. Winter flights coinciding with the northerly wind 'el norte' would carry leafhoppers from the Central Highlands of Mexico to lower elevations close to the Gulf Coast, where winter and spring rains are more common. A return to the central highlands on the rain-bearing trade winds could account for the sudden appearance of D. maidis on seedling maize in June. These findings are consistent with previous observations suggesting a continuum of life style within the genus, ranging from sedentary species of relatively low fecundity and specializing on gamagrasses to D. maidis, a maize specialist.