COTTON LEAF SURFACE-FEATURES SERVE AS BEHAVIORAL CUES TO SILVERLEAF WHITEFLIES

We examined cotton leaves for correlations between surface structures and veins, using light and electron microscopy. Using Bemisia argentif olii Bellows and Perring egg placement, nymphal positions and crawler (first-instar nymph) behavior, we evaluated the responses of whitefly nymphs to leaf surface features. Two kinds of epidermal cells predomin ated the leaf abaxial surface: those underlying vascular bundles and t hose underlying the areoles (regions between veins). Lamina trichomes (simple and complex) originated from elongated epidermal cells overlay ing the veins, including even the most minute (single-stranded) veins. All 2,000 lamina trichomes (non-glandular) that we examined originate d from vascular bundle-associated epidermal cells. Areoles of fully ex panded leaves had perimeters of 2,463 mm (+/- 0.1113 S.E., N = 10) and a mean area of 0.382 mm(2) (+/- 0.0374). Epidermal cells underlying a reoles were isodiametric while those underlying veins were elongated. Eggs were generally deposited on the elongated epidermal cells associa ted with bundles or on cells within ca. 30 mu m of those vascular bund le-associated epidermal cells. Crawlers walked about 2300 mu m per min ute until they settled upon feeding sites that were immediately under the minor veins, never more than about 60-80 mu m from the edge of the abaxial bundle-associated epidermal cells. Crawlers spent at least 80 % of their time in contact with bundle-associated epidermal cells, app arently making contact with these cells either with legs or antennae.