SPECIAL Casale hiiasavivuint 95 
tion, than those dee to securing cross- Eaithawdiba 
But in a few, on the contrary, self-pollination is 
specially arranged for. 
It must be pointed out that the insects which pol- 
linate these specialized flowers have in many cases 
acquired modifications in their structure correspond- 
ing to the modifications in the flowers which they 
frequent. Inthe more specialized forms, indeed, plant 
and animal have become entirely dependent on each 
other; the plants would become extinct in the absence 
of the special insects through whose agency they are 
able by pollination to produce fertile seed; and the 
insects would likewise die out if the flowers to whose 
nectar and pollen they look for food were not 
available. 
As regards the kinds of insects which visit flowers 
for food, these are very numerous and belong to 
almost every section of that large class. In many, 
such as Neuroptera, Orthoptera, Hemiptera, Coleop- 
tera, there is very little special adaptation for their 
flower-feeding habits, and these insects visit flowers, 
such as the Umbellifere, in which the nectar and 
pollen are freely exposed, and lie open to all. Many 
of the Diptera, or Flies, are in the same case; but in 
some families, such as the Bombyliide, high special- 
ization for securing food from flowers is found: the 
creatures are provided with elongated probosces for 
sucking nectar even when it is deeply hidden, and no 
other food is used by the insects in their adult stage. 
But it is among the long-tongued Bees and the 
Lepidoptera (Butterflies and Moths) that the highest 
degree of adaptation in this direction is found; and 
the modifications are associated with those flowers 
