246 



Bulletin 133. 



body about until a smooth cavity or cell is formed. In this 

 earthen cell the caterpillar sheds its skin for the last time and 

 becomes a dark brown, apparently lifeless object — the pupa — 

 shown natural size (at a) and enlarged in figure 71. In the latter 

 part of July last year many farmers reported that the army- worms 



had suddenly left their 



fields and had disap- 

 peared ; this simply 

 meant that they had 

 gone into the ground to 

 pupate. When the 

 worms occur in great 

 numbers, many of them 

 change to pupse under 

 stones, boards, chunks 

 of dirt, or rubbish of 

 any kind, without en- 

 tering the ground ; at 

 such times more or less 

 silk is sometimes spun 

 around the body and 

 particles of earth adhere 

 to it thus forming a slight cocoon. The length of time the insect 

 remains in the pupa state varies with the climate and the season. 

 In the spring and fall the pupa stage apparently lasts from three 

 to four weeks in New York state, while in July only from ten to 

 fifteen days was spent by the insect as a pupa last year. 



Habits of the moth. — Soon after emerging from their cramped 

 quarters in the pupa, the moths gradually expand their wings 

 and may be seen, resting quietly, hidden during the day in the 

 grasses, in the position shown at a in figure 69. The moths 

 usually begin flying about sunset and are doubtlesr. active during 

 the greater part of the night. Their flight is low and is charac- 

 terized by a quick darting motion. Upon first alighting the wings 

 are kept in motion with a rapid quivering for a moment. They 

 do not appear to be as readily attracted by lights as many other 

 moths. In our extensive trap-lantern experiments conducted in 



71. 



• The pupae into zuhich army-worms trans- 

 form. Natural size at a. 



