SEASONAL POLYPHENISM OF ADULT DALBULUS LEAFHOPPERS (HOMOPTERA, CICADELLIDAE)

Leafhoppers from Mexico in the genus Dalbulus exhibit significant seas onal differences in overall body size and coloration as measured by dr y body weight, wing length, and intensity of pigmentation. In the labo ratory, the com leafhopper, Dalbulus maidis (DeLong & Wolcott) and its close relatives, the Mexican com leafhopper, D. elimatus (Ball); D. g elbus DeLong; the fivespotted gamagrass leafhopper, D. quinquenotatus DeLong & Nault; and the Eastern North American species, Baldulus trips aci Kramer & Whitcomb were reared from egg to adult under environmenta l conditions typically found in Mexico during the wet growing season ( young seedlings at 28:20-degrees-C and a photoperiod of 14:10 [L: D] h ) and beginning of the dry winter (mature plants at 23:17-degrees-C an d a photoperiod of 12:12 [L:D] h). Adults reared under environmental c onditions that simulated the beginning of the dry Mexican winter were, on average, 8% larger, 29% heavier, and, except for B. tripsaci, 25% darker in pigmentation than adults reared under conditions typical of the wet summer growing season. Field-collected Dalbulus adults also sh owed seasonal variation in size and color. Dalbulus species, which spe cialize on maize (Zea mays L.), generally exhibited greater seasonal v ariation in color and size than those that specialize on perennial gam agrasses (Tripsacum spp.). Seasonal increase in body size most likely indicates greater storage of energy for survival of harsh conditions a nd possible migration, whereas variation in color may be an adaptation with thermoregulatory and cryptic benefits.