Figure 2.

Mean ± SE weight (mg) of monarch larvae after feeding on treated milkweed discs for 96 h. Treatments included: (a) pollen from event Cbh351 (Cry9C) hybrid G8539Bt that was processed with 250-μm sieve (beginning), pollen from same hybrid processed with 90-μm sieve (finely sifted), and siftings remaining after the initial sample was finely sifted; and (b) no pollen, pollen from event Bt11 (Cry1Ab) hybrid N7070Bt, and pollen from hybrid N7070 (non-Bt) that were processed in the same manner as pollen in a. Mean pollen levels for a and b were ≈600 and ≈900 pollen grains/cm², respectively.