The fact that bumblebees are important as pollenizers of red clover has been established by means of numerous experiments dating from the time of Darwin. Their importance in this respect depends, however, upon their numbers at the time when the clover is in bloom. Thus, in second-year clover, in Illinois, bumblebees are highly important as pollenizers of the second crop, for they are abundant in late July, in August and September. They are unimportant as pollenizers of the first crop, however, for in June the only winged bumblebees in existence are the comparatively few queens that have survived the winter, and these spend a large part of their time in the nest, rather than in the field. The June crop is certainly not pollenized to any considerable extent by bumblebees. In fact, it seldom yields much seed as compared with the second crop in the same locality.

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bumblebees time clover crop pollenizers June fact winter existence queens

Folsom, Justus W.,.POLLINATION OF RED CLOVER BY TETRALONIA AND MELISSODES. 15 (2),181-184.

Folsom, Justus W.,"POLLINATION OF RED CLOVER BY TETRALONIA AND MELISSODES" 15

Folsom, Justus W.,"POLLINATION OF RED CLOVER BY TETRALONIA AND MELISSODES"