The relation between excretory rhythm and water content of honeydew from Cinara pectinatae Nördl and Cinara pilicornis (Hartig) and the honeydew harvesting activity of the honeybee, Apis mellifica L
Preliminary observations of Cinara pectinatae honeydew harvesting by honey bees show that honeydew harvesting activity varies throughout the day. The honeydew excretion activity of Cinara pectinatae and Cinara pilicornis was studied using a revolving plate that allowed honeydew droplets excreted in 24 h to be counted. Maximum excretion occurs between 20 00 and 24 00 h and a minimum excretion between 12 00 and 15 00 in C pectinatae (fig 1A). In C pilicornis there does not appear to be a circadian rhythm of honeydew excretion (fig 1 B). Refractometer measurements of the proportion of honeydew dry matter show that the dry matter content of freshly excreted honeydew varies between 52% and 78%. We also found a negative correlation between the relative hygrometry and the honeydew dry matter content (fig 2). It was noted that dry matter content increases during the morning until 12 00 h, is stable during the early afternoon at a high value and decreases after 16 00 h (fig 3). The study of honeydew harvesting activity shows that honey bees collect honeydew at a high level from 10 00-11 00 h during warm and dry weather (fig 3 a, b, c, d, f) and from 12 00-14 00 h during raw weather (fig 3 g, h). Thus, the drying of the honeydew during the day and the honeydew excretion rhythm are 2 factors which apparently limit the harvesting of honeydew by the honey bee
