to be 262 days, which lacks four and a half days of being the same 

 as the recorded average duration of the larval stage of P. vandinei. 



The lengths of larval stages of two individuals reared through 

 from egg to pupa were, respectively, 242 and 252 days, both below 

 the average for the species. 



The First Instar. — This instar of the grub, computed from six 

 records, had an average duration of 32 days, a maximum of 40 days, 

 and a minimum of 26 days. During this instar the grub increases 

 in length from about 6-7 millimeters, when first hatched, to 18 

 or 19 millimeters at the end of the instar. The breadth of head 

 varies from 1.9 to 2.1 millimeters. 



Tlw Second Instar. — This, computed also from o])servations of 

 six individuals, had an average duration of 61 days, a maximum 

 of 93 days, and a minimum of 43 days, w'hich makes the second 

 instar of the grub of this species appear to be much longer than 

 the corresponding instar of the sugar cane white-grul). This is 

 due to the small number of individual records upon which the av- 

 erage is based, two of the six having required in excess of two months 

 (one of them over three months) to pass the instar, which is ab- 

 normally long. True averages can be secured only from large num- 

 bers of observations, which will require additional study in the case 

 of this species. The average length of instar from four records 

 not exceeding two months in length was 50 days, which is nearer a 

 correct average. 



In length the grul) increases, during the second instar, from about 

 18 to 30 millimeters, and the head varies in breadth from 3.3 to 

 3.6 millimeters. 



77(6 Third Inslar. — This instar of tli.' grub, as in the case of the 

 preceding species, is taken as including the pre-pupal stage and is 

 figured as the time elapsing between the second molt and the date 

 of pupation. The pre-pupal stage seldom exceeds a week in any of 

 the Porto Rican species of PJujUophaga. 



The average duration of tlie third instar, from records of two 

 reared grubs, was 169 days. The time recpiired by each oT the 

 grubs was respectively, 164 and 174 days. To gain accurate knowl- 

 edge of the average duration of this instar will require the rear- 

 ing of additional grubs in confinement. 



The lengtli of grub increases in the third instar from about 30 to 

 46 millimeters, and the head varies from 5.5 to 6.2 millimeters in 

 breadth. The average breadth of head, computed from seventeen 

 grubs of an average lengtli of 39 millimeters, was 5.78 millimeters. 



148 



