FERTILIZATION OF FLOWERS BY INSECTS... 295 
Among flies the proboscis of Bombylius discolor is 10 millime- 
tres long ; that of Rhingia rostrata from 11 to 12 ™: ; among bees 
that of Bombus hortorum is 21 ™™, and that of Anthophora pilipes 
25™"; the proboscis of Sphinx Elpinor among the Lepidoptera is 
from 20 to 24 ™: long, that of Sphinx pinastri from 28 to 32 ™™, 
and that of Sphinx ligustri from 37 to 42 ™™ But the Lead 
proboscis is that of Sphinx convolvuli which is from 70 to 80 ™:, 
This exceptional size led me to infer that Sphinx convolvuli may 
have acquired its long proboscis by competition with the flies and 
bees with a long proboscis inhabiting warm climates. This con- 
jecture is confirmed by information as to the geographical distri- 
bution of Sphinx convolvuli afforded me by Dr. Speyer. 
In order to eliminate the visits of bees and flies which prey 
upon pollen and permit only those of Lepidoptera, a variation still 
more advantageous than the elongation of the melliferous tube is 
manifestly that of flowering at night. And this is precisely what 
many plants do, which keep their flowers closed during the day and 
open them in the evening when with the disappearance of the sun 
the activity of bees and flies is entirely destroyed. It is in the 
hours of the evening and night that the flowers of such plants by 
the brilliancy of their colors and the pungency of their odors at- 
tract sphinxes and other moths, showing in an eloquent way how 
advantageous to themselves is the preference they show for 
the visits of insects which are only useful to those of insects which 
are at the same time useful and hurtful. But it will be said; why 
cannot bees and flies as well as Lepidoptera adapt themselves part _ 
passu to the noctifloral variations of plants? It is not difficult to 
see why. Lepidoptera feed only upon honey, and hence are obliged 
to follow pari passu the variations of the plants which nourish them 
with analogous variations on their part. Flies, however, do not 
live exclusively upon honey, but suck by instinct any sort of liquid, 
and bees after collecting honey and pollen have to make compli- 
cated manipulations in the hive. Whence it is plain why Lepidop- 
tera only and not bees and flies as well, can acquire al 
habits, and adapt themselves to night-flowering plants.* 
* However ingenious and seductive may be the theory here developed by the author 
to explain the genesis of evening or nocturnal flowers, so flowers with a long, 
honar Verne tube, it nevertheless seems contradicted by a multitude of facts col- 
and by argumen 
The whole theory of the author reposes upon the fact that Lepidoptera do not feed 
