THE CHINCH BUG. 19 
drawn up. The relative abundance of the eggs upon the stalks and 
upon the roots may be changed somewhat, as Dr. Thomas has pointed 
out, by the character of the soil. Where the soil is very damp the 
majority of the eggs are doubtless laid upon the stalks, whereas if the 
earth is dry and easily penetrated the great majority of them will 
be found upon the rootlets and upon the stalks beneath the ground. 
According to Professor Riley the eggs hatch on the average in two 
weeks. The young larve begin to take nourishment as soon as possi- 
ble after hatching. They insert their beaks sometimes even before they 
emerge from the earth, but more often crawl up the stalk before be- 
ginning to pump. They growl with considerable rapidity and swarm 
over the stalk upon which they were born, walking about with ease 
and wandering from one stalk to another if occasion demands. As we 
have already shown, four molts are undergone before the insect reaches 
the perfect state, and generally from five to seven weeks elapse from 
thehatching tothe final molt. Dr. Shimer’s repeated observations show 
that at Mount Carrcll, [lL., the imago usually appears in from fifty- 
seven to sixty days after the laying of the eggs, and about forty-two days 
from the hatching of the larve. By the time the majority of theinsects 
of this first generation are full-grown, or even before, the wheat has 
become too hard to offer them much nourishment, or harvest time has 
arrived, and they begin to migrate in search of food. Neighboring corn- 
fields offer a more tempting diet, and in seasons of great abundance 
they march in numerous colonies, moving by a common impulse from the 
wheat to the corn. Strange to say, although the commoner form pos- 
sesses wings the insect does not generally take flight, but prefers to walk 
along the ground. Occasionally, however, at this time they take wings 
and scatter. This, however, is rarer when the insects are plentiful than 
when they are comparatively scarce. Under no circumstances will 
these insects take flight to escape danger. Dr. Shimer says: 
No threatening danger, however imminent, whether of being driven over by grain- 
reapers, wagons, or of being trodden under foot, will prompt it to use its wings to es- 
cape. I have tried all imaginable ways to induce them to fly, as by thrashing among 
them with bundles of rods or grass, by gathering them up and letting them fall from 
a height, etc., but they invariably refused entirely to use their wings in escaping from 
danger. : 
The migration takes place often, and, according to some authors, 
usually before the majority of the brood have attained full growth. 
There are always many immature individuals among a large host, and 
often the army is composed almost entirely of such. In fact, at these 
times there is apt to be a general confusion of so-called larva, pupe, 
and adults, owing to the fact that some hibernating females oviposit 
much in advance of others and to the other fact, previously mentioned, 
that a single female takes several days or even weeks to lay all of her 
eggs. Professor Forbes records egg-laying presumably by hibernating 
individuals from the last week in May (at Decatur) until the last week in 
June (at Warsaw), thus making certain individuals of the first brood one 
