THE SUGAR-CANE MOTH BORER. 



PUPA. 



27 



The pupa at first is dirty white, about the same color as the 

 hibernating larva, with faint purplish longitudinal stripes. It 

 gradually hardens, and darkens, and in an hour or two becomes 

 mahogany brown. As the time for emergence approaches the pupa 

 darkens more and may become almost black. 



The pupa is quite active when disturbed, being able to thrash 

 about with its abdomen, which gives it a rolling, squirming motion. 

 A touch or a jar will cause this action, as will also the placing of the 

 pupa in direct sunlight in summer. Placed in the sun, a pupa 

 squirmed about till it reached a shady place. 



DURATION OF PUPAL PERIOD. 



The first pupae in the spring are formed from overwintering 

 larvae in April or May, and pupa? may be found from this date to 

 December. Few larvae pupate after the middle of November, those 

 which have not pupated prior to this time hibernating as larvae. 

 Nearly 200 larvae were collected in cane cut for the mill on December 

 2-4, 1915, but no pupae were found in all the stalks cut open. Adults 

 have emerged from pupae in the insectary as late as December 5, but 

 a large percentage of those which did not pupate until late and had 

 the pupal period prolonged by cold did not emerge. 



The pupal period, like that of the larva, has a w,ide variation, from 

 6 to 22 days being required for the emergence of the adult, with an 

 average of 8J days throughout the year. The pupae which produced 

 male moths required on an average 8.8 days for emergence, and those 

 which produced females 8.4 days. Often there is a variation of 2 to 

 3 days among pupae which transform on the same date. The data 

 are presented in Table VI and figure 9. 



Table VI. — Relationship of mean temperature to the developmental period in 

 the pupal stage of the sugar-cane moth borer. 



Period. 



Average 

 mean tem- 

 perature. 



Number 

 of records. 



Period. 



Average 

 mean tem- 

 perature. 



Number 

 of records. 



Days. 



5 



6 



7 



8 



9 



10 



11 



12 



° F. 

 77.1 

 82.3 

 81.1 

 81.3 

 80.9 

 76.6 

 76.1 

 74 



3 



27 

 153 

 92 

 42 

 19 

 12 

 4 



Days. 

 13 

 14 

 15 

 16 

 17 

 18 

 19 

 22 



° F. 

 71.6 

 79.7 

 73.9 

 77 

 72 



69.8 

 84.6 

 63.7 



1 

 7 

 5 

 5 

 1 

 1 

 3 

 1 



DURATION OF THE LIFE CYCLE. 



The length of the life cycle varies considerably with the tempera- 

 ture. Taking the minimum of each immature stage, the sum of 28 

 days is obtained, while in the same way a maximum of 293 days is 



