A simple gravimetric technique for estimating honeydew or nectar production

We describe a simple gravimetric technique for measuring the standing crop or production of carbohydrate-rich solutions such as honeydew or nectar. Simulated honeydew was sampled by absorbing droplets of solutions of known concentration and volume with dried and weighed pieces of filter paper. The change in mass of the paper after redrying provides an estimate of the total solution carbohydrates. This method was compared with a widely-used technique, whereby the volume and concentration of droplets is measured with microcapillary tubes and a sugar refractometer. A factor was derived to convert gravimetric refractometer readings (g sucrose 100 g -1 solution) to volumetric carbohydrate concentration (g carbohydrate 100 ml -1 solution) for the simulated honeydew solutions. There was no difference in the ratio of measured-to-expected carbohydrate mass between the two techniques, showing that the quick, easy, and accurate filter-paper method is appropriate for measuring carbohydrate-rich solutions.