17 
tent that it could have been rolled up as a carpet. In 1875 I 
noticed in my own yard the species exhibiting at the same time 
these two traits or habits. In one portion of the area they were at 
work as Cut-worms, while an army was marching across another 
portion from an adjoining yard, the two bodies not commingling or 
having any connection with each other. Those acting as Cut-worms 
were paler and much less distinctly marked than the others; they 
were also larger wffien fully grown. In order to be certain as to 
my determination, I traced them to the perfect state; the moths 
sent to Prof. Riley for examination in 1876 were of the number de¬ 
veloped from these Cut-worms. 
This fact enables us to understand why it is they are not <?b- 
served in the non-migratory years, as at this time they are acting 
the role of the Cut-worm, and are hid from view, but it renders the 
solution of the question, Why do they march in armies? the more 
difficult. 
The habits of the worms are somewhat similar to those of the 
ordinary Cut-worms, as they avoid the hot sun, coming forth to 
feed chiefly in the night or during cloudy days, hiding during the 
hot and sunny portion of the day under the clods, stones and other 
rubbish. They prefer rather cool weather, and as will hereafter be 
shown, appear to be more abundant in damp seasons, (following a 
previous dry year) than in hot dry years. When in excessive num¬ 
bers they may be observed feeding throughout the day,, unless the 
sun shines quite warm, which scarcely ever fails to drive them to 
their hiding places. I have observed them trying to march when 
the sun was hot; if an open and especially a dusty space, as a 
road, lay in their pathway, numbers would perish before crossing it, 
and in some instances the entire army recoiled from the attempt 
and turned back. An instance of this kind occurred near our town, 
where an army made an attempt to cross a roadway in 1875, dur¬ 
ing the hot part of the day, but after large numbers had perished 
turned back to the field from whence they came; at least they 
failed in the effort and retreated to the shade of the fence. An 
open croquet ground lay in the pathway of the little army that en¬ 
tered my yard. I noticed that few that entered upon it (being a 
clear sunny day) succeeded in crossing it; those which could not 
reach the grass at the sides perished from the heat of the sun. In 
this case most of the worms were not more than half , grown. 
During their life in the larval state, which, as.we will show, lasts 
about four weeks or a month, they change their skin five times; 
and having completed their growth, descend into the ground a 
few inches below the surface, where they are soon transformed into 
a pupa or chrysalis. They spin no cocoon, but by movements of 
the body and the excretion of a sticky fluid usually form a kind of 
earthern cell; but occasionally they simply crawl into some hiding 
place to undergo their transformations. 
2 
