HISTORICAL. 129 



to the flowers of a single species during one journey from the hive or nest. 

 Detto (1905) pointed out that constancy may be used to refer to the fact 

 that a bee visits only flowers of one species on a journey, or to fidelity to 

 one species until it obtains nothing more from it, when it goes to another. 

 It must also be recognized that single individuals seem to visit only certain 

 portions of very large or very floriferous plants and that they do not go to 

 other plants of the same species, but to a new species when a particular 

 portion has been exhausted. Moreover, nothing is known as to whether a 

 bee gives the preference to flowers of the same color or shade as those upon 

 which it began to collect. The term "monodrome constancy" may be 

 applied to the cases where the bee visits the flowers of but one species during 

 a single flight, and "polydrome constancy" to those where successive 

 flights are always directed to the same species as long as this yields nectar 

 or pollen. An insect that then goes to another species is "temporarily 

 constant" in contrast to one that confines itself chiefly to one species. 



Early observations of constancy. — Two chance observations only 

 have been recorded for the period before Darwin, one by Aristotle and the 

 other by Dobbs (1736). Aristotle stated that during each flight the honey- 

 bee does not settle upon flowers of different kinds, but flies, as it were, from 

 violet to violet and touches no other species till it returns to the hive. 

 With respect to constancy, Darwin (1876:415) says: 



"All kinds of bees and certain other insects usually visit the flowers of the same 

 species as long as they can, before going to another species. It may be observed by any 

 one, both with hive and humble bees, in every flower garden; not that the habit is 

 invariably followed. Humble and hive bees are good botanists, for they know that 

 varieties may differ widely in the color of their flowers and yet belong to the same 

 species. Some species of diptera or flies keep to the flowers of the same species with 

 almost as much regularity as do bees, and when captured they are found covered with 

 the pollen. I do not know whether lepidoptera generally keep to the flowers of the 

 same species, but I once observed many minute moths apparently eating the pollen 

 of Mercurialis annua. I then went to a female plant some yards off and saw three of 

 these moths light on the stigmas. It must not be supposed from these several state- 

 ments that insects strictly confine their visits to the same species. They often visit 

 other species when only a few plants of the same kind grow near together. That 

 insects should visit the flowers of the same species as long as they can is of great 

 importance to the plant, as it favors the cross fertilization of distinct individuals of 

 the same species, but no one will suppose that the insects act in this manner for the 

 good of the plant. The cause probably lies in the insects being thus enabled to work 

 quicker; they have just learnt how to stand in the best position on the flower, and how 

 far and in what direction to insert their proboscides." 



Kerner (1876) stated that the bumble-bee always devotes itself to the 

 plunder of a single species at one time, but in commenting on this, Weed 

 (1884) said that he had observed one bumble-bee fly back and forth from 

 Pedicularis canadensis to Vicia americana, another from hyacinth to col- 

 umbine, a third from Solomon's seal to dandelion, and a fourth from vetch 

 to honeysuckle. Forbes (1878) recorded 30 visits in succession of Bombus 

 to Lamium, during which it ignored all other flowers, while Syrphus visited 

 Rubus to the complete neglect of Lamium. Kronfeld (1888:785) observed 

 a honey-bee that returned for 10 visits to a bed of cucumbers after being 



