1924] 
Flower Visits of Insects 
103 
of flowers which they visit, it will be found that those which 
before July are eutropic, hemitropic or allotropic, are hemitropic 
after June. Really the highest specialized and latest developed 
flowers and insects are hemitropic. 
Specialization for obtaining Nectar. — The ruby throat, the 
Lepidoptera, long-tongued bees and some siphonate flies can 
visit a great many flowers from which short-tongued bees are 
excluded. They are at some disadvantage on flowers with 
shallow nectar. 
Muller (3,58) states that A pfs and Bomhus play by far the 
most important part in the fertilization of German indigenous 
flowers. Knuth (2,154) says: “Just as the pollen-collecting 
apparatus has reached its highest degree of development in 
Apis and Bomhus, so also has the mouth of the bees become 
best adapted for rifling the nectar of flowers. It is therefore 
intelligible that bees belonging to these two genera play a far 
more important part than any other insects in the pollination of 
our indigenous flowers.’’ When these bees are compared with 
other bees having a similar flight, the importance of the special- 
ization of the proboscis and scopa is not so obvious. When 40 
species of Halictidse make nearly as many visits as 133 species of 
long-tongued bees, it is not on account of a more highly special- 
ized tongue or scopa. The Halictidoe visit 14 more flowers and 
make 1123 more visits than the Bombinse, 927 more than Bom- 
binse and Apis together. When Apis and Bomhus make only 
13.3 per cent of the visits recorded in Muller’s Fertilisation of 
flowers, it is not easy to understand these statements regarding 
their importance in pollination. 
Dependence on a Floral Diet. — The food of bees is almost ex- 
clusively from flowers. The fig chalcids and Pronuba are about 
the only insects which can compare with them. The importance 
to flowers of the nest-provisioning habit is shown by the fact 
that the nest-making bees average 23.4 visits, while the in- 
quilines average 10.7. The females of the nest-makers average 
20.6 visits, while the males average 10.3. The females of the 
inquilines average 8 . 8 and the males 8 . 0. 
