(11/17. Dr. Ogle 'Pop. Science Review' April 1870 page 167. Mr. Farrer 'Annals and Magazine of Natural History' 4th series volume 2 1868 page 258. Mr. Belt in a letter to me.) I noticed in 1861 exactly the same fact with Trifolium pratense. So persistent is the force of habit, that when a bee which is visiting perforated flowers comes to one which has not been bitten, it does not go to the mouth, but instantly flies away in search of another bitten flower. Nevertheless, I once saw a humble-bee visiting the hybrid Rhododendron azaloides, and it entered the mouths of some flowers and cut holes into the others. Dr. Hermann Muller informs me that in the same district he has seen some individuals of Bombus mastrucatus boring through the calyx and corolla of Rhinanthus alecterolophus, and others through the corolla alone. Different species of bees may, however, sometimes be observed acting differently at the same time on the same plant. I have seen hive-bees sucking at the mouths of the flowers of the common bean; humble-bees of one kind sucking through holes bitten in the calyx, and humble-bees of another kind sucking the little drops of fluid excreted by the stipules. Mr. Beal of Michigan informs me that the flowers of the Missouri currant (Ribes aureum) abound with nectar, so that children often suck them; and he saw hive-bees sucking through holes made by a bird, the oriole, and at the same time humble-bees sucking in the proper manner at the mouths of the flowers. (11/18. The flowers of the Ribes are however sometimes perforated by humble-bees, and Mr. Bundy says that they were able to bite through and rob seven flowers of their honey in a minute: 'American Naturalist' 1876 page 238.) This statement about the oriole calls to mind what I have before said of certain species of humming-birds boring holes through the flowers of the Brugmansia, whilst other species entered by the mouth.
The motive which impels bees to gnaw holes through the corolla seems to be the saving of time, for they lose much time in climbing into and out of large flowers, and in forcing their heads into closed ones. They were able to visit nearly twice as many flowers, as far as I could judge, of a Stachys and Pentstemon by alighting on the upper surface of the corolla and sucking through the cut holes, than by entering in the proper way. Nevertheless each bee before it has had much practice, must lose some time in making each new perforation, especially when the perforation has to be made through both calyx and corolla. This action therefore implies foresight, of which faculty we have abundant evidence in their building operations; and may we not further believe that some trace of their social instinct, that is, of working for the good of other members of the community, may here likewise play a part?
Many years ago I was struck with the fact that humble-bees as a general rule perforate flowers only when these grow in large numbers near together. In a garden where there were some very large beds of Stachys coccinea and of Pentstemon argutus, every single flower was perforated, but I found two plants of the former species growing quite separate with their petals much scratched, showing that they had been frequently visited by bees, and yet not a single flower was perforated. I found also a separate plant of the Pentstemon, and saw bees entering the mouth of the corolla, and not a single flower had been perforated. In the following year (1842) I visited the same garden several times: on the 19th of July humble-bees were sucking the flowers of Stachys coccinea and Salvia grahami in the proper manner, and none of the corollas were perforated. On the 7th of August all the flowers were perforated, even those on some few plants of the Salvia which grew at a little distance from the great bed. On the 21st of August only a few flowers on the summits of the spikes of both species remained fresh, and not one of these was now bored. Again, in my own garden every plant in several rows of the common bean had many flowers perforated; but I found three plants in separate parts of the garden which had sprung up accidentally, and these had not a single flower perforated.