HONEYDEW. A term applied to the sweet ish secretion which under certain conditions drips from the water-pores of the leaves of some trees. It is a form of 'bleeding' appears only when an abundant supply of moisture (re ducing evaporation) and a high temperature per mit the development of a considerable sap-pres sure in the live cells. Sonic kinds of manna are the dried honeydew or the saccharine exudations of certain plants. Very generally this exuda tion, ns it. dries, coats the surface of leaves and branches with a clammy film, to which every thing brought by the atmosphere adheres, thus closing the pores of the plant and impairing its hen 1th.
The Wane honeydew is often applied to a saccharine secretion of certain insects. notably the plant-lice, the fleadiee (Psyllidic), certain scale-inscets and white flies (Aleyrodid,e), and eertain leaf-hoppers or tree-hoppers. Of the lat ter, Proconia (Oncometovial undrlia secretes the most abundant supply, and is the cause of the phenomenon often described as 'weeping trees.'
The honeydew secreted by all of these insects is frequently very abundant, giving the foliage and bark of trees a glistening appearance. and fre quently attracting swarms of bees, ants. wasps, and other honey-loving insects. It is usually secreted from the anus, and with the tree-hoppers is ejected forcibly in a spray, or several small drops at frequent intervals, so that a tree in which they are very numerous appears to be 'weeping.' Honeydew affords a welcome filth's for the spores of certain of the smut-fungi, and an affected tree is likely soon to become black with smut. Thus an olive orchard in California or Southern Europe, the leaves of which turn black, will surely he found to be infested with a scale-inseet (Leranium clew) which secretes a quantity of honeydew. Orange and lemon plantations sometimes suffer great injury from the abundance of honeydew: and it has been proved a cause of very great loss in the coffee plantations of Ceylon. See APHID.