LIFE HISTORY. 



While the life-history of PJiyllopJiafja [xnioriccnsis has not been 

 studied to the extent and with tlie thoroughness of the preceding 

 species, such studies as have been uuide clearly indicate tliat the 

 entire generation of the .species is passed in one year, and that 

 there is sufficient variability in the length of life-cycle to give rise 

 to a considerable overlai)ping of ])roods, if indeed the species may 

 be said to have broods. The seasons of appearance in abundance 

 seem to depend largely upon conditions of rainfall, which would 

 indicate that the stage of the life-cycle displaying the greatest varia- 

 tion in length, next to the third instar of the grub, is the period 

 during wliich the newly issued adult is in the pupal cell in the soil, 

 awaiting the proper soil conditions (i. e., of moisture) to dig to the 

 surface and emerge for feeding and egg laying. 



A single individual of the species was reared through from egg 

 to adult, recpiiring for the transformation (from date of laying of 

 egg to date of issuing of adult) two hundred and seventy -six and a 

 lialf days. 



The average time required to undergo these transformations, 

 found by adding together the averages for the several stages of the 

 insect, each secured from a number of records, was 2961/2 days; 

 the maximum duration, by adding together the maximums of each 

 stage, 343 days; the minimum, 268 days. Reduced to months, these 

 figures show an average egg-to-adult period of approximately 10 

 months, a maximum of III/2 months, and a mininmm somewhat 

 under 9 months. If larger numbers of individuals had been reared 

 through the various stages, the latitude of variation would undoubt- 

 edly have been increased. 



The Egg Stage. 



The description of the egg and the method of laying given for 

 the sugar cane white-grub (P. rroidiiiri) will s(M-ve ('(jually well for 

 Ibis one. 



The average length of the egg stage (fi'oiu tlate of laying to date 

 of liatching), from records of the hatcliing of fifty-four eggs kept in 

 confinement, was computed to ix' 13'/. days, with a maxinuim period 

 of 16 days and a mininmni of 12 days. The length of this stage 

 is practically the same as for P. vaiKlinei. 



The Wiiitk-Grib, or Lau\.\i- Stac^e. 



The average duration of the lai-val stage of /'. ix^iioricf iisis, ol)- 

 tained by adding the average lengths of the three instars, jii'oved 



147 



