GENERAL HABITS. 19 
dence pointing to the trend of its distribution. (See discussion under 
Cicadula 6-notata, pp. 97-99.) 
It is extremely probable that some of the native species that 
occur in moderate numbers on various native plants have been stim- 
ulated by the introduction of cultivated crops which have furnished 
them a fresh food supply, so that they have increased greatly in num- 
bers and have become of more importance from an economic stand- 
point than would have been true in their connection with native 
plants. Most of our species, especially those that attack cultivated 
crops, have a wide range of food plants. Some, however, are re- 
stricted verj r closely to certain genera or species of plants as hosts. 
GENERAL HABITS. 
There are several features in the general habits of these insects 
which may be discussed together, although there are certain ones 
in which each particular species must be considered by itself. In their 
food habits, as has been mentioned, there is a wide diversity, some 
species affecting a great variety of plants, others a very few. The 
various species, however, agree pretty generally in attacking the leaves 
or the freshly grown portions of the stem of the plant, making their 
punctures where they can secure the sap with the greatest ease, thus 
affecting the growth, of the more succulent portions. In many in- 
stances the insect shows a distinct adaptation to certain parts of 
the plant, so that the shape and color of the body blends in with the 
part upon which it is feeding. This is the most noticeable in the 
case of certain species which are marked so that the colors blend with 
certain portions of the plant, notably in cases where this coincides 
with the markings at the joints of the stems, instances being known 
where such blending causes the most perfect resemblance of the insect 
to the joint. Some of the insects affect the seeds or blossoms, others 
cluster near the ground, and some have even been reported as affecting 
the roots, but this must be exceptional as very few have been noted to 
attack the plant in this manner. There is no distinct adherence to a 
particular plant except during the nymphal stages or for certain 
species which have aborted wings and are therefore unable to fly; 
practically all the species, however, jump with great facility and if 
disturbed will leave the plant and come to rest either on the ground 
or some adjacent plant. 
General migration of the insects is not common, but there must be 
local migrations from field to field, especially at times when the food 
supply becomes scarce or unsuitable on account of the ripening of the 
plant. At such times we may have a general dispersal of the insects; 
for instance, from wheat fields to adjacent grasslands, or in autumn 
from grasslands to adjacent fields of fall wheat, oats, rye, etc., which 
furnish a much more attractive food for that season. Migrations in 
