Seasonal Polyphenism of Adult Dalbulus Leafhoppers (Homoptera: Cicadellidae)

Abstract

Leafhoppers from Mexico in the genus Dalbulus exhibit significant seasonal differences in overall body size and coloration as measured by dry body weight, wing length, and intensity of pigmentation. In the laboratory, the corn leafhopper, Dalbulus maidis (DeLong & Wolcott) and its close relatives, the Mexican corn leafhopper, D. elimatus (Ball); D. gelbus DeLong; the fivespotted gamagrass leafhopper, D. quinquenotatus DeLong & Nault; and the Eastern North American species, Baldulus tripsaci Kramer & Whitcomb were reared from egg to adult under environmental conditions typically found in Mexico during the wet growing season (young seedlings at 28:20°C and a photoperiod of 14:10 [L:D] h) and beginning of the dry winter (mature plants at 23:17°C and a photoperiod of 12:12 [L:D] h). Adults reared under environmental conditions 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 showed seasonal variation in size and color. Dalbulus species, which specialize on maize ( Zea mays L.), generally exhibited greater seasonal variation in color and size than those that specialize on perennial gamagrasses ( Tripsacum spp.). Seasonal increase in body size most likely indicates greater storage of energy for survival of harsh conditions and possible migration, whereas variation in color may be an adaptation with thermoregulatory and cryptic benefits.