Vol. xxiv] ENTOMOLOGICAL NEWS. IO5 



that Epeolus is not a parasitic genus, and expresses an entire 

 absence of doubt as to the correctness of this conclusion. Dr. 

 Graenicher has shown (Bull. Wis. Nat. Hist. Soc. } 3:164) 

 that Triepeolus helianthi is an inquiline of Melissodes trinodis. 

 In 1910 Prof. Cockerell in "An Introduction to the Study of 

 Rocky Mountain Bees" (Univ. Col. Studies, 7: 183) described 

 Triepeolus Rob. as a parasitic genus, but Epeolus sens str. is 

 not thus characterized. In this locality I have never taken 

 either sex of Triepeolus donatus except on the flowers of the 

 Compositae. It can not be competition for pollen which leads 

 this species and one or two others of the same genus to visit ex- 

 clusively the inflorescence of this family. Evidently it is the 

 attractiveness of the flowers. 



In Southern Maine both sexes of Halictoidcs novae-angliae 

 year after year visit exclusively the flowers of the pickerel 

 weed; and I, therefore, call the species monotropic in this 

 locality. Because in another region, where the pickerel weed 

 is absent, it visits other flowers, Robertson ^vould not regard 

 it as monotropic anywhere. This is a matter of definition in 

 which we differ. If a bee in a certain region visits only one 

 species of flower for pollen I would consider it monotropic in 

 that area, and I believe that this usage should prevail. It 

 seems probable that any oligotropic bee, which extends into 

 a region where the flowers it habitually visits elsewhere do not 

 occur, will resort to other flowers. Robertson would seem 

 formerly to have held a similar opinion for he says (Bot. Gaz., 

 28:34), "When the flowers upon which a bee depends become 

 extinct or rare, the bee may disappear or be forced to resort 

 to flowers which originally it did not visit." 



I am aware of the so-called analogy presented by other 

 groups of organisms to oligotropism ; and in my article men- 

 tioned certain Lepidoptera and Coleoptera, which live on a 

 single plant species both in the larval and adult stages ; yet the 

 oligotropic habit does not appear so obvious to me as to Rob- 

 ertson. The honey bee, bumble bees and many other bees visit 

 a great variety of flowers and the natural expectation would 

 be that all bees are polytropic. Certainly this is what most 



