"Mr. Knight once observed," says Bevan, "a shower of honey-dew descending in innumerable small globules, near one of his oak-trees, _on the 1st of September_; he cut off one of the branches, took it into the house, and holding it in a stream of light, which was purposely admitted through a small opening, distinctly saw the aphides ejecting the fluid from their bodies with considerable force, and this accounts for its being frequently found in situations where it could not have arrived by the mere influence of gravitation. The drops that are thus spurted out, unless interrupted by the surrounding foliage, or some other interposing body, fall upon the ground; and the spots may often be observed, for some time, beneath and around the trees affected with honey-dew, till washed away by the rain. The power which these insects possess of ejecting the fluid from their bodies, seems to have been wisely instituted to preserve cleanliness in each individual fly, and indeed for the preservation of the whole family; for pressing as they do upon one another, they would otherwise soon be glued together, and rendered incapable of stirring. On looking steadfastly at a group of these insects (_Aphides Salicis_) while feeding on the bark of the willow, their superior size enables us to perceive some of them elevating their bodies and emitting a transparent substance in the form of a small shower." "Nor scorn ye now, fond elves, the foliage sear, When the light aphids, arm'd with puny spear, Probe each emulgent vein, till bright below, Like falling stars, clear drops of nectar glow." _Evans._ "The _willow_ accommodates the bees in a kind of threefold succession; from the flowers they obtain both honey and farina;--from the bark propolis;--and the leaves frequently afford them honey-dew at a time when other resources are beginning to fail." "Honey-dew usually appears upon the leaves as a viscid, transparent substance, as sweet as honey itself, sometimes in the form of globules, at others resembling a syrup; it is generally most abundant from the middle of June to the middle of July, sometimes as late as September." "It is found chiefly upon the _oak_, the _elm_, the _maple_, the _plane_, the _sycamore_, the _lime_, the _hazel_, and the _blackberry_; occasionally also on the _cherry_, _currant_, and other fruit trees. Sometimes only one species of trees is affected at a time. The oak generally affords the largest quantity. At the season of its greatest abundance, the happy humming noise of the bees may be heard at a considerable distance from the trees, sometimes nearly equalling in loudness the united hum of swarming."