THE CANADIAN BNToMOLOGIST. 32'? 



On page 41 Pierce says: "The majority of the hosts known are 

 flower-frequenters, and are classed as oligotropic when visiting a single 

 species, genus or family of flowers, and polytropic when visiting many 

 genera or famiHes of flowers. It is very reasonable to infer that the 

 most ordinary method of transfer of triungulids takes place at flowers, 

 because of the analogous forms of strepsipterous and rhipiphorid triun- 

 gulids. Most of the wasps are flower-visitors, because they can quench 

 their thirst in the nectarine liquids. They are consequently polytropic ; 

 but the bees are more highly developed, and often specially adapted for 

 particular flowers, hence many of them are oligotropic." Loew introduced 

 these terms to distinguish bees like Bombus, which fly all season and visit 

 a great variety of flowers, which he called polytropic, from bees like 

 Anthophora^ which have a short flight and visit comparatively few flowers, 

 which he called oligotropic. He calls the females of Halictiis polytropic, 

 and the males, which appear late and fly a shorter time, oligotropic. In 

 their visits for nectar bees resemble other flower-visitors, but in the visits 

 of the females for pollen to provision their nests, bees show their essential 

 bionomic relations to flowers and their essential differences from other 

 insects. Tlierefore, being the first to use Loew's terms, at least in English, 

 I limited the term oligotropic to bees which collect pollen from flowers of 

 some particular natural group, and the term polytropic to those which use 

 pollen from unrehted flowers. (Bot. Gaz., XXVIII, 27,29, 1899) I 

 have recorded 56 cases of these oligotropic bees. Of these only 20 are 

 limited in their nectar visits also. Of 17 local stylopized Andrenid?e, only 

 one is oligotropic in the sense used by Pierce. iMost of the 20 are oligo- 

 tropes of Compositae. It is not so surprising that some of these are exclu- 

 sive when we consider that at their maximum the Compositoe form 34 per 

 cent, of the indigenous blooming flowers. I do not regard statements that 

 a bee is oligotropic, unless made by a person who has made a great num- 

 ber of observations on flowers, and who distinguishes whether the feniales 

 collect the pollen or not. Wasps have never been called polytropic 

 except by Pierce. If these terms are applied to wasps, they should he 

 used to distinguish wasps which provision their nests with insects of the 

 same natural group from those which use an indiscriminate variety of 

 insects for that purpose. 



On flowers wasps are hardly polytropic in any sense. I have observed 

 1,949 flower visits of 208 species. The ones making 40 or more visits are ; 

 Scolia bicincta, 40 ; Eumenes fratermis, 41 ; Polistes metriciis. 43 ; Sphex 

 vulgaris, 46; Myzine sexcincta, 50; Polistes variatus, 5 1 ; Sphex inter cepta, 



