Certain families of the Hemiptera whose members feed on the sap of plants are capable of excreting, without prior digestion, excess water and carbohydrates which they cannot metabolize. This fluid is voided via the anus, and is known as honey-dew. It contains a mixture of invert sugars and dextrin (Wrigglesworth, 1950). In the case of Eriococcus on manuka the insects living on the leaves and branches excrete this honey-dew, which is washed down the plant by dew and rain. Some of this solution is caught in the weft of the mycelium, where it is eventually used by the fungus as a source of energy. The honey-dew may be washed off manuka trees, and it is not uncommon to find plants and even the soil beneath diseased trees covered with the black fungus.