With respect to the number of flowers which bees visit in a given time, I observed that in exactly one minute a humble-bee visited twenty-four of the closed flowers of the Linaria cymbalaria; another bee visited in the same 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 Oenothera was visited eight times by several humble-bees, and I followed the last of these bees, whilst it visited in the course of a few additional minutes every plant of the same species in a large flower-garden.  In nineteen minutes every flower on a small plant of Nemophila insignis was visited twice.  In one minute six flowers of a Campanula 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 alluded to bees biting holes in flowers for the sake of obtaining the nectar.  They often act in this manner, both with endemic and exotic species, in many parts of Europe, in the United States, and in the Himalaya; and therefore probably in all parts of the world.  The plants, the fertilisation of which actually depends on insects entering the flowers, will fail to produce seed when their nectar is stolen from the outside; and even with those species which are capable of fertilising themselves without any aid, there can be no cross-fertilisation, and this, as we know, is a serious evil in most cases.  The extent to which humble-bees carry on the practice of biting holes is surprising:  a remarkable case was observed by me near Bournemouth, where there were formerly extensive heaths.  I took a long walk, and every now and then gathered a twig of Erica tetralix, and when I had got a handful all the flowers were examined through a lens.  This process was repeated many times; but though many hundreds were examined, I did not succeed in finding a single flower which had not been perforated.  Humble-bees were at the time sucking the flowers through these perforations.  On the following day a large number of flowers were