Dear Bilal,

CS are polysaccharides with a dissaccharidic repeating unit.

regards

Hello,

I have been waiting to see if anyone had anything better than what I did--watch and count. I do not understand Dr. Michaud's reply but that is probably my deficiency and not his.

Watching and counting works but it is slow. Also, the rate changes with food, time of day, relative humidity and more. 

In any case, here are a couple of papers that might address your question.

“THE EXCRETION OF HONEY-DEW BY TUBEROLACHNUS SALIGNUS(GMELIN) (HOMOPTERA: APHIDIDAE)”, T.E. Miller. Proceedings of the Royal Entomological Society of London. Series A, General Entomology, Volume 33, Issue 4-6, pages 49–55, June 1958

“A mutation in amino acid permease AAP6 reduces the amino acid content of the Arabidopsis sieve elements but leaves aphid herbivores unaffected” by Emma Hunt, Stefano Gattolin, H. John Newbury, Jeffrey S. Bale, Hua-Ming Tseng, David A. Barrett, and Jeremy Pritchard, J Exp Bot. 2010 Jan; 61(1): 55–64.

@Joe Olechno

Thank you very much for help me. Actually I also didn't understand the answer of @Philippe Michaud.

I am not sure what can be the purpose of counting of honeydew droplets by an aphid like S. avenae! It is a visual exercise and touch upon the physical and chemical properties of honeydew produced in aphids due to obligate feeding on phloem sap. Physical property of honey dew will depend on the relative concentrations of water and nutrients present in it but chemical property will depend on the quantity and quality of soluble sugars present according to host plant phenology. 

Notwithstanding the science of honeydew in aphids, to be able to count the droplets will require one to (i) measure the diameter and length of the cornicle which exude honeydew and (ii) to determine the density of honeydew. Once these parameters are known, then one can apply the principle of capillary action and ascertain the number of droplets that are dropped by releasing capillary pressure. This procedure is not likely to exactly replicate the true exudation of honeydew by aphids, but certainly would provide an approximate idea.