76 Bulletin Wisconsin Natural History Society. [Vol. 7, Nos. 1-2. 



species just considered. (C. altissimum) so closely that a further 

 description is unnecessary. Insects to the number of 24 were ob- 

 served as follows : 



EUTEOPOUS. 



Bees : 4, worker, s. and e. p. ; 7, worker, s. and c. p. ; 9, male and 

 worker, s. and c. p. ; 17, female, s. and e. p. ; 20, male, s. ; 23, male 

 and female, s. and e. p. ; 33, female, s. and c. p. ; 34, female, s. and c. p. 



HEMITEOPOUS. 



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

 Flies : 303 ; 307— both f. p. 



Butterflies and moths: 447; 448; 453; 4.54; 468; 469; 480; 481; 

 492— all s. 



ALLOTEOPOUS. 



Beetles: 516; 517 — both f. p. 



Eutrop 8 = 33.3% 



Hemitrop 14 = 58.4% 



Allotrop 2 = 8.3% 



37. Cirsium arvense (L.) Seop. Canada Thistle. 



The flowers of this troublesome weed, a native of Europe, have 

 been observed from June 22 to September 27. Of this species also 

 we have an account published by H. Mueller 35 , and later observa- 

 tions by various European authors. Gynodicecism (pseudoher- 

 maphrodite pistillate and staminate flowers on different plants) 

 has been reported from different parts of Europe, but I have not 

 come across any such distribution of the sexes in the plants of 

 our surroundings. The color of the florets varies from purplish 

 to white, but the first named is the prevailing one. The slender 

 lobes of the corolla are 4 l / 2 mm. long, and the bell-shaped upper 

 part of the tube has a width of 1 mm. at the entrance, and a 

 length of i]/ 2 mm. A distinct sweet odor renders the flowers 

 rather attractive to insects; the following 113 species of which 

 were taken : 



EUTEOPOUS. 



Bees : 1, worker, s. and c. p. ; 5, worker, s. and c. p. ; 7, worker, 

 s. and c. p.; 11, worker, s. and c. p.; 12, worker, s. and c. p.; 13, 

 worker, s. and c. p.; 17, female, s. and c. p.; 18, female, s. ; 23, female, 

 s. and c. p.; 34, female, s. and c. p.; 35. male, s. ; 41, female, s. and 

 c. p. ; 59, female, s. 



35) H. Mueller, loc. cit, pp. 3S7-3S9. 



