FERTILIZATION OF FLOWERS BY INSECTS. A 283 
two pollen-masses attached. Ascending from the bottom towards 
the top, it visited the second and third flowers of the same spike. 
After withdrawing its head from the third flower, it stopped a 
short time and endeavored to brush off the pollen-masses with its 
legs, but without success. It then continued its visit, climbing up 
the spike, and visited a fourth flower. At this point I tried to 
catch it in the net, but failed, and it flew away. After standing a 
short time we saw a Bombus hortorum visit three or four flowers 
from base to summit of a spike of Orchis mascula, after which it» 
flew to another individual of the same species, visiting its flowers 
in the same way. Upon examining the stigmas of this second 
individual we found pollen scattered upon them, and the anther 
lobes emptied of their pollen-masses. In the space of about two 
hours, which we spent in observing this fecundation of Orchis mas- 
cula, we noted two visits of Bombus lapidarius and one Psithyrus 
campestris. The Bombus lapidarius did not remain-in the flowers — 
longer than from two to three seconds. We captured the Psithyrus 
and one Bombus lapidarius. Both.had a quantity of pollen-masses 
upon their heads, some of which were already depressed upon their 
respective stalks, and therefore in a condition to rub against and 
fecundate the stigmas, while others were yet erect and therefore not 
in a condition to effect fecundation. Of ninety-seven bees collected 
by us in this excursion, thirty-two had pollen-masses stuck upon 
their heads. Sometimes we observed that the bees succeeded in 
freeing themselves from some of the pollen-masses, either by tear- 
ing them off with their mandibles or brushing them off with their 
fore-legs. Possibly, it is in this way that sometimes in the flowers 
of Orchis, pollen-masses are found in greater or less proximity to 
the stigma, out of place and, as it were, wasted. 
At least a good third, then, of the bees collected on the heights 
of Stromberg were engaged in the fecundation of Orchises, and 
we can obtain an approximate measure of their activity by the 
_ following figures. At seven o’clock, A. M., in a meadow contain- 
ing several thousand individuals of Orchis mascula, I collected 
ten spikes which had one hundred and seyen open flowers, only 
three of which had the stigma smeared with pollen, and one alone 
was without pollen-masses. Towards five o "clock, . F: M., I collected 
with pollen, two of which still preserved the pollen-masses in 
