Twelfth Report op the State Entomologist 205 



In their marches the caterpillars move, so far as possible, in a nearly 

 straight line, turning aside for nothing that can be surmounted. It has 

 even been stated that they will climb the trunk of a tree to the lowest 

 fork and descend on the other side. A number of instances have been 

 reported in which they marched over buildings, where in some instances 

 they were so thick as to«cover the sides of the structure. They can not 

 bear the hot sun, and so far as possible, avoid it in their travels, and 

 after crossing a sunny field they may be seen resting in the shade of 

 fences or shrubbery that may offer the desired relief. Water does not 

 deter them. The rear ones push forward over the bridge formed by the 

 dead and dying of the vanguard: if it be a large running stream they 

 perish by the millions. Their march is not a very rapid one; it has been 

 computed at, ordinarily, the rate of 30 yards an hour. 



Occasionally it happens, that the army-worm will migrate from the 

 fields for the sole purpose of finding a suitable place for pupation, as in 

 instances when there is abundant food in a grain field, but the soil is too 

 hard for the caterpillars to bury in easily. This was noticed to a limited 

 extent in the outskirts of Albany, where after partly stripping the leaves 

 in an oat field, the caterpillars in migrating, inflicted little damage to a 

 corn and grass field adjacent, but later their pupae were found in abund- 

 ance under the leaves and grasses beside the outer fence — 35 being 

 counted within an area of about two square feet. 



Associates. — It is not an uncommon occurrence, that cut-worms are 



associated with the army-worm in its ravages. In the nth Illinois 



Report, Mr. Coquillett records the presence of Agroiis c-nigrum in an 



army-worm attack, in the proportion of one cut-worm to eight or ten 



army-worms, while Dr. Howard found the proportion to be as high as 



one to five.* A single example of Agrotis ypsilon, was detected in a 



lot of over 100 army-worms received from Ghent, N. Y., early m October 



of the past year. 



Food of the Caterpillars. 



The favorite food of the army-worm is undoubtedly, the green succulent 

 leaves of a luxuriant growth of some member of the true grass family, 

 the Graviinece. In fields of small grain, the greener leaves are quickly 

 stripped from the stalk, and, if the stem is not too hard, the heads will 

 frequently be eaten off and fall to the ground. Occasionally, the heads 

 are partly eaten after they they have been lopped off, but more fre- 

 quently they are left untouched by the caterpillars. This wanton habit 

 of the army-worm, increases its harmfulness in grain fields, without any 



*In -^rd Rept. U, S. Entomological Commission 1883, p. 135. 



