a week to ten da.ys immediately preceding the pubation of the grub. 

 In our figures, therefore, the pre-pupal stage is considered as included 

 in the third instar of the grub. 



The average duration of larval period from the sum of the average 

 lengths of the three separate instars, was 233 days; the maximum, 

 295 days; the minimum. 174 daj^s. Reduced to months, this gives 

 an average duration of 7% months, a maximum of 9% months, and 

 a minimum of 5% months. 



The average length of the larval stage, obtained from the six indi- 

 vidual grubs that successfully reached the pupal stage, was 245 days, 

 which was twelve days in excess of the average for the species. This 

 was due, it is believed, to the fact that the soil in the cage in which 

 these five grubs were reared was allowed to become very dry at times, 

 for periods of weeks, which retarded the growth of the grubs to a 

 marked degree. 



The First Instar. — The average duration of this was 24 days, 

 the maximum 35 days, and the minimum 13 days, computed from a 

 total of sixty records of reared grubs. 



In measurement, the first-instar grub varies in length from about 

 5 millimeters, when first hatched from the egg, to a maximum length 

 of 12 or 13 millimeters. 



The average diameter of the head, from measurements of thirty-* 

 two grubs whose average length was 11.3 millimeters, was found to 

 be 1.33 millimeters. 



The Second Instar. — The average duration of the second instar was 

 found to be 31 days, or just a month; the maximum 39 days; the 

 minimum, 23 days. These figures are from the records of tliirty- 

 eight individual grubs reared through this instar. 



The length of the grub in the second instar increases from 12 

 or 13 millimeters just following the molt, to a maximum of 20 or 

 21 millimeters. The average width of head, from measurements of 

 thirty-three grubs whose average length was 15.7 millimeters, was 

 found to be 2.38 millimeters. 



The Third Instar. — The average length of the last instar. taken 

 from six grubs that reached the pupal stage, was found to be 178 

 days; the maximum, 221 days; the minimum, 138 days. Or. re- 

 duced to months, the average was 6 months, the maximum 7% months, 

 and the minimum about 4i/> months. 



In length, the third instar grub increases from about 20 to about 

 31 or 32 millimeters. The average width of head, from measurements 

 of five grubs whose average length was 25 millimeters, was found 

 to be 4.09 millimeters. 



156 



