1999] Oraenichcr, Wisconsin Flowers and Their Pollination. 51 



as in the four preceding ones no crossing of the stylar branches 

 takes place. 



The following 46 visitors were observed at the flowers : 



EUTEOPOUS. 



Bees : 1, worker, s. and c. p. ; 2, female and worker, s. and c. p. ; 

 4, female and worker, s. and c. p. ; 7, male and worker, s. and c. p. ; 

 9, male, s. ; 13, male and female, s. ; 15, female, s. ; 16, male and female, 

 s. ; 17, female, s. and c. p.; 24, female, s. and c. p.; 34, male and female, 

 s. and c. p. ; 35. male and female, s. and c. p. ; 56, female, s. 



Hawk-moth : 484, s. 



HEMITEOPOUS. 



Bees: 99, female, s. ; 100, male and female, s. ; 104, female, s. ; 

 118, female, c. p.; 135, male. s. 

 Wasp : 186 s. 

 Flies: 272; 283; 298; 306; 307; 313;' 315; 318; 319; 322; 332— all 



s. or f . p. 



■ Butterflies and moths: 448; 450: 451; 460; 463; 464; 467; 469; 



474 ; 481 ; 485 ; 493— all s. 



ALLOTROPOUS. 



Flies : 372 ; 376— both f . p. 



Bettle : 527, f . p. 



Eutrop 14 = 30.5% 



Hemitrop 29 = 63.0% 



Allotrop 3= 6.5% 



Eupatorium L. 



Three species are represented in the flora of Milwaukee Coun- 

 ty, two of them with white, and the third with purple flowers. 

 They differ in the length of the tubal florets, and accordingly we 

 find a different set of visitors in each of the three. In view of the 

 fact that the white species with the shortest tube(B. perfoliatum),, 

 and the purple one with the longest tube (B. purpureum ) are found 

 growing together in profusion, and blooming synchronously, and 

 are consequently exposed to exactly the same insect fauna, they 

 are fits objects for comparison in regard to the effect of tube length 

 and color on the visitors. 



10. Eupatorium perfoliatum L. Boneset. 



This species has a flowering season extending from about 

 July 22 to September 16. A head is 3 to 4 mm. wide, and is 

 made up of 12 to 15 white sweet-scented florets. By the grouping 



