THE ARMY HABIT 65 



It grows rapidly in size. At the end of a week it moults or 

 casts its skin, a process in which the old skin splits open along 

 the back and the worm crawls out, clothed in a new skin that 

 had developed beneath the old one. Again it feeds as before, 

 its voracity increasing with its size. This moulting is repeated 

 four or five times during the month after the worms hatch, so 

 that by the end of this period the insect is an inch and a half 

 long, and has the familiar markings of the full-grown army 

 worm . 



The instinct of the worm now teaches it to seek more secure 

 shelter for the helpless stage upon which it is about to enter. 

 It burrows into the soil an inch or less and wriggles about in 

 the earth until it produces a hollow cell. In this it casts its 

 skin again and becomes a pupa — the third st^ige of its existence. 

 When the worms are very abundant, many of them do not 

 go into the ground but change to pupte beneath whatever shel- 

 ter may be at hand. About a fortnight later, another change 

 takes place, and the fully-developed moth emerges from the 

 pupa, thus completing the round of the insect's life. The 

 moths fly towards dusk and at night, and by means of their long 

 tongues, coiled up when not in use, they suck the nectar of 

 various flowers. 



The moths sometimes seem attracted bv buildings. I have 

 been told of their swarming toward the close of cloudy after- 

 noons about barns and outbuildings ; and early in August, this 

 year, they were trapped by thousands in the projecting porch 

 of Thompson Hall. VVe killed one thousand of these moths, 

 placed them in a little heap, and photographed them. The 

 photograph is reproduced on the title page of this bulletin. It 

 represents the moths about one-half natural size, and seems a 

 small pile, but had the moths not been killed there might have 

 developed from them in September nearly half a million army 

 worms. 



THE ARMY HABIT 



During ordinary years the armv worm is present in most of 

 the regions where its outbreaks occur, individual worms feed- 

 ing here and there in meadows and pasture lands, but the 

 number is not sufficient to attract notice. At such times their 



