THE LESSER CORN STALK-BORER. 15 



PROCESS OF HATCHING. 



Shortly before the larva is ready to emerge it can be seen very 

 distinctly through the semi transparent shell. The brown-black 

 head and the pinkish markings on the segments especially are con- 

 spicuous. The larva occupies a curled position inside of the shell, 

 with its head resting on the ultimate and penultimate segments of 

 the body. Just preceding emergence a wavelike rhythmic motion 

 is seen, starting at the head and continuing from segment to segment 

 slowly to the end of the body, after which the larva moves its head 

 about and with its mandibles makes an incision large enough for it 

 to pass through. This takes about five minutes. The larva then 

 usually rests a few minutes, after which it begins to draw itself out 

 of the shell. 



NUMBER AND LENGTH OF INSTARS AND LENGTH OF LARVAL LIFE. 



The number of instars and their length, as well as the total length 

 of the larval life, are extremely variable, as will be noted by referring 

 to Tables IV, V, and VI. These variations are due in part to differences 

 of temperature. During the summer months the larvae may molt 

 four or five times and in fall five or six, making from five to six instars 

 for the former and six to seven for the latter. The seventh instar in 

 such instance resembles the sixth in color pattern and size. The 

 second instar and sometimes the third is somewhat longer than 

 the first during the summer months. In fall, however, the first instar 

 is longer than any of the others, except the last one, or the one just 

 preceding pupation, which is generally also the longest during the 

 summer months. 



The length of the life of the larva is somewhat dependent upon the 

 number of instars. The larger the number of instars the larva under- 

 goes, the longer the period it will take in reaching maturity, as is 

 brought out by comparing the averages of the instars in Tables 

 IV, V, and VI. In Table IV the larvae having five instars reached 

 maturity in 374.5 hours, while those having six instars reached 

 maturity in 406.33 hours. In Table V those having five instars 

 reached maturity in 397 hours, as compared to 453 hours for the 

 six-instar larvae. In Table VI the six-instar larvae required 842 hours 

 while the seven-instar larvae required 906 hours to reach maturity. 



The larvae may reach maturity in the short period of 13.8 days, but 

 generally in about 16.8 + days, during the summer months. How- 

 ever, one larva required as many as 20.8+ days to reach maturity. 

 In fall, when temperatures are low, this period is considerably 

 lengthened, varying from a minimum of 22.0+ to a maximum of 41.6 

 days. 



