Patterns of honeydew droplet production by nymphal stages of Bemisia argentifolii (Homoptera: Aleyrodidae) and relative composition of honeydew sugars

Honeydew droplets were collected from nymphal and adult Bemisia argentifolii Bellows and Perring. Nymphs produced a regular pattern of honeydew droplets consisting of periods of production followed by periods where no droplets were produced. The mean length of individual production periods increased from the second (40 +/- 1 min) to the fourth (162 +/- 11 min) stadium, until the late fourth stadium when honeydew production by most nymphs became continuous. In contrast, the periods of no production decreased in length as nymphs developed from the second (35 +/- 1 min) to the fourth (23 +/- 1 min) stadium. The frequency of droplets during the production periods decreased from the first (80 +/- 1 drops per h) to the fourth (22 +/- 1 drops per h) stadium. This periodic pattern is consistent with previous reports for Trialeurodes vaporariorum (Westwood), however, the functional significance of this pattern remains unknown. if this cyclic pattern should prove critical to the successful feeding and development of whiteflies, its disruption may decrease survival and provide a novel target for pest control strategies. Second and third instars had higher percentages of di- acid trisaccharides (sucrose, trehalulose, and melezitose) and lower percentages of monosaccharides (fructose and glucose) compared to first and fourth instars. This could indicate a change in metabolic needs of nymphs during periods of rapid growth, or indicate that trehalulose synthase producing endosymbiotic bacteria are more abundant, or more actively producing enzyme during the second and third stadia.