50 



most cases tlie caterpillars in each of these armies must have been num- 

 bered by the millions; even an approximate estimate of the worms of a 

 single army would have been im])racticable. Oftentimes when an army 

 was marching across a lane or I'oadway, nearly the entire surface of the 

 ground for several rods would be covered by a mass of worms; one could 

 not step without crushing several of them/' They feed mostly at night 

 and on cloudy days, although not by any means refraining from travel 

 and feeding in bright weather. 



Geogroph'ical Distribution. — The army-worm is ajjjxirently a North 

 American species, and was well known in New England before the Revo- 

 lution, where, indeed, measures for the arrest of its movements were 

 ado])ted which are still the best we can suggest. The species is now 

 distributed throughout nearly the whole world, but it is only in the 

 United States east of the Rocky Mountains and in ('anada that it nuilti- 

 plies to a number such as to comj)el its movements (7i masse in search of 

 food. It is particularly abundant throughout the regioii from Iowa and 

 Maine to Texas, Alabama, and North Carolina, and in this i-egion there 

 is rarely a year in which it does not somewhere become numerous enough 

 to do serious injiuy. 



Life History of the Artny-worm. — The yearly history of the species is 

 not fully known as yet, some diversity of opinion prevailing as to the 

 stage in which it hibernates. Many accurate observations on this sub- 

 ject relate to partly grown caterpillars found late in fall, winter, or early 

 spring, and hibernation in this stage seems to be a somewhat general 

 occurrence. On the other hand, we have taken the moth in March in 

 Illinois, and have once seen it connnon at lights on April 11. It is 

 also said by Prof. John B. Smith to have been found in New Jersey 

 during the entire winter in sheltered places. We have seen no satisfac- 

 tory evidence of its hibernation in the pupa stage, although this fact is 

 likewise asserted by some. 



When a brood of the caterpillars becomes full grown they rapidly dis- 

 appear, entering the ground an inch or so, and forming there smooth 

 cavities by twisting about, or making a slight cocoon under clods or 

 other shelter. There they change to smooth brown pupae (See PI. II), 

 from which later the moths emerge. 



The eggs for the first generation are laid, in our latitude, about the 

 middle of May. These hatch in from eight to ten days. The life of the 

 caterpillar is twenty to thirty days; that of the pupa, twelve to fifteen 

 days; and the moths begin oviposition about a week after they emerge. 

 This gives about seven to eight weeks for the life cycle in midsummer. 

 The eggs (See PI. II) are placed by the mother moth behind the sur- 

 rounding sheath of the leaf of grass or grain, from ten to fifty or more 

 together, imbedded in a gummy substance which fastens them also to the 

 leaf surface and closes the sheath around them. It is said that " early 



