EXPERIMENTAL-ANALYSIS OF FLIGHT ACTIVITY OF 3 DALBULUS LEAFHOPPERS (HOMOPTERA, AUCHENORRHYNCHA) IN RELATION TO MIGRATION

The flight periodicities of three species of Dalbulus leafhoppers were monitored in a controlled-environment chamber using Johnson-Taylor se gregating suction traps. To assess their effect on flight activity, ph otoperiod and host plant age were experimentally manipulated to mimic conditions at different seasons in central Mexico. All three species f lew during the crepuscular periods. Comparisons of the flight periodic ity of the three species suggested that the maize specialists, D. maid is (DeLong & Wolcott) and D. elimatus (Ball), are more likely than D. gelbus DeLong (a gamagrass [Tripsacum spp.] and maize feeder), to fly from mature maize plants at the end of summer. The second flight of th e 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 s pecies D. maidis displayed a lesser tendency to leave old maize in aut umn than the high elevation endemic, D. elimatus. However, the flight behavior of D. maidis is consistent with winter (short photoperiod) mi gratory 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 r ains are more common. A return to the central highlands on the rain be aring trade winds could account for the sudden appearance of D. maidis on seedling maize in June. These findings are consistent with previou s observations suggesting a continuum of life style within the genus, ranging from sedentary species of relatively low fecundity and special izing on gamagrasses to D. maidis, a maize specialist.