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Show 424 HABITS OF INSECTS CHAP. XI. c:tnd of any sweet fluid, and as they do not disdain t~e 1ninute drops on the glands of Prunus laurocerasus, It is a strange fact that they do not suck the. nectar of many open flowers, which they co~l~ do without the aid of a proboscis. Hive-bees v1s1t t:1e flowe~s of the Sy1nphoricarpus and Tritoma, a~d. th1s makes It all the stranger that they do not VISit the flowers of the Epipactis, or, as far as I have seen, those of the Scrophularia aquatica; although they do visit the flowers of Scrophularia nodosa,, at least in North .r\..merica.* The extraordinary industry of bees and the number of flowers which they visit within a short time, so that each flower is visited repeatedly, must greatly increase the chance of each receiving pollen from a distinct plant. When the nectar is in any way ~1iclden, bees cannot tell without inserting their proboscides whether it has lately been exhausted by other bees, · and this as remarked in a forn1er chapter, forces them to visit many more flowers than they otherwise would. But t.hey endeavour to lose as little time as they can; thus in flowers. having several nectaries, if they :find one dry they do not try the others, but as I have of~en observed, pass on to another flower. They work so Industriously and effectually, that even in the case of social plants, of which hundreds of thousands grow together, as with the several kinds of heath, every single flower is visited, of which evidence will pres~ntly be given. They lose no tiD;le and fly very quickly from plant to plant, but I do not know the rate at. which hive-bees fly. Humble-bees fly at the rate of ten miles an hour as I was able to ascertain in the case of the 1nales fr~m their curious habit of calling at * 'Silliman's American Journal of Science,' Au~. 1871. CHAP. XI. IN RELATION TO CROSS-FERTILISATION. 425 c:rtain fixec~ points, which made it easy to 1neasure th time .taken In passing from one place to another. W 1 th respect to the n urn ber of flowers which bees visit in a given time, I observed that in exactlv on minute a humLle-bee visited twenty-four of the dlos fl flowers of the Linaria cyn~balaria; another bee visited in the sa1ne time twenty-two flowers of the Symphoricarpus racemosa; and another seventeen flowers on two plants of a Delphinium. In the course of fifteen minutes a single flower on the summit of a plant of CEnothera was visited eight times by several humblebees, and I followed the last of these bees, whilst it visited in the course of a few additional 1ninutes every plant of the same species in a large flowergarden. In nineteen n1inutes every flower on a small plant of Nemophila insignis ·was visited twice. In one minute six flowers of a Can1panula were entered by a pollen-collecting hive-bee; and bees when thus employed work slower than when sucking nectar. Lastly, seven flower-stalks on a plant of Dictamnus fraxinella were observed on the 15th of June 1841 during ten minutes; they were visited by thirteen humble-bees each of which entered many flowers. On the 22nd the same flower-stalks were visited within the same time by eleven humble-bees.. This plant bore altogether 280 flowers, and from the above data, taking into consideration how late in the evening humble-bees work, each flower must have been visited at least thirty times daily, and the same flower keeps open during several days. The frequency of the visits of bees is also sometimes shown by the manner in which the petals are scratched by their hooked tarsi ; I have seen large beds of Mimulus, Stachys, and Lathyrus with the beauty of their flowers thus sadly defaced. Perforation of the Corolla by Bees.-I have already |
