1909] Graenicher, Wisconsin Flowers and T.heir Pollination. 41 



Co., Wis., and 64 species of insects taken at the flowers. All of 

 the species were numerically poorly represented, with the excep- 

 tion of the Syrphid-flies Bristol is transversa*, and E. meigenii, 

 which were quite in evidence. 



It has been previously pointed out how an increase in long- 

 tongued visitors runs along with an increase in tube length of the 

 florets. The following table contains the average percentages ( al- 

 lotropous, hemitropous, and eutropous visitors) for different tube 

 lengths. I have arranged the species of Composite discussed in 

 this paper in 6 groups. The earliest species Antennaria ncglecta 

 appears together with an insect-fauna of quite a different make-up 

 than the fauna of late spring and summer, as set forth above, and 

 this species is therefore not considered along with the others in 



the table. 



Allotr. 

 % 



1/0 — 1 mm 55.5 



114—2 mm 32.9 



2y 2 — 3 mm 23.0 



3y 2 — 4 mm 7.4 



41/2—5 mm 12.2 



6 mm 7.1 



To this I add a table with the average percentages for the but- 

 terflies and moths ( Lepidoptera ) . 



Lepidoptera. 

 % 



1/,— 1 mm 2.4 



iy 4 — 2 mm 8.7 



2y 2 — 3 mm 9.4 



31/3—4 mm 19.1 



41/2—5 mm 26.9 



6 mm 33.4 



There is a decrease in the short-totiTned (allotropous) visitors 

 from 55.5% to 7.1%, and an increase in the long-tongued bees* 

 from 3.1% to 37.2%. The hemitropous visitors occupying an in- 

 termediate position between the other 2 groups show in general a 

 moderate increase. Of course we can not expect the figures de- 

 rived from our observations to show a steady increase or decrease 

 corresponding to every slight difference in tube length, and ac- 

 cordingly we sometimes run across an increase where a decrease 

 is expected, and vice versa. This is due to more than one reason. 

 In the first place it must be kept in mind that a list of visitors is 



* For a tube length of 3%-4mm., the average of 30.2% for the eutronous 

 visitors refers to the long-tongued bees plus 1 hawk-moth (a visitor of Aster 

 novw-avglifr). 



The figure for the long-tongued bees alone is 29.7%. 



