1923] 
Flower Visits of Insects 
161 
ference in the length of the proboscis, but is largely a phenological 
matter connected with the late flight of the workers, after May 
13, still later flight of the males, after July 4, and the late bloom- 
ing of B' which is really a phenological class. The males only 
resemble bees in general in preferring B' in their late visits. 
The percentage of visits to B' after June is for the females 32.1, 
workers 38.1, and males 57.6. So that under the same con- 
ditions all three forms prefer B'. The females show a maximum 
under Ma, 47.3, while the workers and males show maxima under 
Mas, 43.5 and 57.8. 
Seven species, forming 4 per cent of the long-tongued bees, 
make 23 per cent of the long-tongued bee visits, the average 
being 102. Bomhus americanormn makes 227 visits, the highest 
number for any visitor. Bumblebees are the characteristic 
visitors of long-tongued bee flowers and have probably had more 
influence in producing such flowers than all other bees together. 
They make 39 per cent of the visits to Ma, the highest specialized 
of non-social flowers. 
Psithyrus . — Of 47 visits to 39 flowers, 61.7 per cent are to 
Mas, 87.2 to social flowers, 42.5 to Compositse, 14.9 to Labiatse 
and 12.7 to Leguminosse. 
Loew (2, 103) says: “the habit possessed by female bumble- 
bees of chiefly seeking out hymenopterid flowers, while the 
males give preference to social flowers, is exaggerated in the 
parasitic genus Psithyrus^ which constitutes a small side-branch 
of the group. The species of this genus consequently prefer 
dark-colored flowers even more than do the short-tongued species 
of Bomhus.” 
The European visits for the females show 34.3 more in 
percentage of visits to Hb than to B', while the local visits show 
only 6.0 more. In the local species the apparent preference for 
red flowers is not a consequence of a preference for Hb or of any 
difference in the visits of the males, for, while the males show 
33.3 more in percentage of visits to B' than the females do, they 
also show 15.1 more in percentage of visits to red. Local visits 
to red are 55.3 per cent, in the Berlin Garden 71.5, Low Germany 
74.0 and the Alps 77.8. The visits of the males which fly late, 
do not differ from those of the females as much as the late visits 
