FERTILIZATION OF FLOWERS BY INSECTS. 287 
they die with hunger; and on the 17th of May, of this year (1869) 
I saw two dead individuals of Andrena parvula in the flowers of 
Cypripedium. ` 
I here leave the first part of my subject, the application of the 
Darwinian doctrine to flowers, and pass to the second, which is 
the application of the same doctrine to the insects which visit the 
flowers. 
As flowers are accommodated to the visits of insects, and as the 
meaning of the structure of flowers can only be comprehended by 
thoroughly knowing their entomological relations, so the insects 
which derive nutriment from flowers are accommodated to them, 
and the structure of their bodies cannot be well understood except 
in the relation of adaptation to flowers. And since, according to 
the Darwinian doctrine, the adaptations of insects to floral food 
can only be considered as characteristics slowly acquired by heredi- 
tary descent, we are necessarily led to distinguish inferior or ` 
primitive, and superior or posthumous forms. We are. thus led to 
some indications of a genealogical tree of the insects which visit 
flowers. 
These insects belong principally to three orders, the Hymenop- 
tera, Diptera and Lepidoptera. The incentives, however, which 
urge them to visit flowers are different for each. The Lepidoptera 
suck honey exclusively; the Diptera devour pollen and are in 
the habit of sucking not only honey, but any sort of liquid; and, 
finally, the Hymenoptera which visit flowers, that is, bees, feed ex- 
clusively on honey and pollen, not-only in their perfect state, but 
also as larvee, so that they suck honey, eat pollen, and collect both 
for their young. 
Of the three orders cited, that of Lepidoptera is the only one 
which is composed of families all of which are adapted to floral 
food, although only in the perfect state. Hence, it is that their 
buccal organs have a very uniform structure. The labrum and 
mandibles are entirely atrophied ;* the maxille are transformed 
into two tubular [nearly], cylindrical and spirally twisted fila- 
ments which perform the function of a sucking tube; and at the 
base of these filaments are two rudimentary palpi. The inferior 
lip or labium is atrophied, and as a compensation its palpi are 
ie developed. 
*Their rudiments are ae sige ear peers certain silk-worm moths, in which the 
Geny is eonia] atrophied. — 
