Table 2.

Frequency distribution of pollen density levels on milkweed leaves inside a cornfield and at different distances from the cornfield edge (0 m)

Pollen density, cm2	Inside a cornfield	From edge of cornfield
		0 m	1 m	2 m	4–5 m
0–100	0.527	0.833	0.900	0.974	0.996
100–200	0.170	0.093	0.062	0.024	0.004
200–300	0.101	0.033	0.022	0.000
300–400	0.072	0.017	0.006	0.002
400–500	0.041	0.008	0.002
500–600	0.041	0.007	0.002
600–700	0.021	0.002	0.001
700–800	0.009	0.002	0.000
800–900	0.009	0.003	0.001
900–1000	0.002	0.001	0.000
1000–1100	0.000	0.001	0.001
1100–1200	0.003		0.000
1200–1300	0.001		0.001
1300–1400	0.000
1400–1500	0.000
1500–1600	0.002
Average	170.6	63.1	35.4	14.2	8.1
Sample size	1456	1265	1107	422	1056

Based on data from sampling dates at 50–100% anthesis (days 6 and 11 for Ontario 2000 and days 6, 9, and 14 for Maryland 2000).