THE CRANBERRY ROOTWORM. 5 



flood is drawn in the spring. Soon after the water is drawn the larvas 

 commence to feed again, which may be noted by the fresh barking of 

 the roots. Before commencing to pupate the larvae move closer to 

 the surface of the bog, the majority being found in the first inch of 

 soil. Some idea of their abundance was obtained by counting the 

 larva? under plats of soil 10 inches square. Twelve larva? were obtained 

 in one instance and other counts of 1 1 and lesser numbers were made 

 where the injury to the vines was quite apparent. From the fore- 

 going it will be seen that the species spends most of its life in the larval 

 stage, or approximately 10 months. Possibly some of the larva? fail 

 to mature at the expiration of this period and spend another year in 

 the bog before reaching the adult stage. 



PUPAL STAGE. 



The time when pupation commences varies somewhat with the 

 management of the bog. The earlier the flood is drawn the earlier 

 will be the date of general pupation. In 1913, when the water was 

 drawn April 1, pupa? were in the majority June 6; while in 1914, 

 when the water was drawn May 20, the larva? outnumbered the pupa? 

 two to one on June 15. Pupation studies were carried on in wooden 

 cages having glass bottoms, which permitted one to observe those 

 larva? which formed cells against the glass. The average duration 

 of the pupal stage was found to be 14 \ days, and from 2 to 3 days were 

 spent by the adult hardening in the cell and reaching the surface. 



SUMMARY OF LIFE HISTORY. 



Stage. 



Period of usual occurrence, i Range in occurrence. 



Usual 

 duration. 



Range in 

 duration. 



Adult 



June20-Aug. 1 June 6-Oct. 20 



July 10-30 ; July 10-Sept. 3 



Jurie?0-30 ' May 25-July 9 



Days. 

 35 



8 



"1 



Days. 

 56 





6-11 



Larva 



Pupa 



13-17 



RECOMMENDATIONS FOR CONTROL. 



Some way in which to control an insect infestation by the use of 

 water usually first suggests itself to one connected with the cranberry 

 industry. The particular bog, however, upon which most of the obser- 

 vations were made has an insufficient water supply limited to a win- 

 ter flooding with no available water for reflooding. Late holding of 

 fehe wai rr that is, until May 20 — had no effect in reducing the infes- 

 tation. The larvae were in as good condition after this treatment as 

 when, the year previous, the water was drawn April t. Laboratory 

 lerimente have shown that the Larva can live submerged in clean 

 water for as long as 41 days, while pupa' have not, survived more than 

 u daj . Examination of a bog which had been reflowed for a period 

 of i daye i;i the latter pari of May disclosed many live larva hut, no 



