44 



THE GEAPE ROOT-WOEM. 



Table XIX. — Percentage of 2-year-old larvse of the grape root-worm as recorded in 

 vineyards in the vicinity of North East, Pa., in the fall of 1909. 



Vineyard in silt soil in the valley. 



Vineyard on loamy soil in the 

 valley. 



Vineyard on gravelly loam on 

 the hill. 



Date of 

 digging. 



Num- 

 ber of 

 vines 

 exam- 

 ined. 



Total 

 num- 

 ber of 

 larvse. 



Per- 

 centage 

 of old 

 larvse. 



Date of 

 digging. 



ber^ Total 

 IfJ^ num- 

 PxJm l^erof 

 iSld.' >'^^^- 



Per- 

 centage 

 of old 

 larvae. 



Date of 

 digging. 



Num- 

 ber of 



vines 

 exam- 

 ined. 



Total 

 num- 

 ber of 

 larvse. 



Per- 

 centage 

 of old 

 larvse. 



Aug. 17 



to 

 Oct. 12 



32 



328 



3.0 



Aug. 16 



to 

 Sept. 20 



I 18 1 449 



0.66 



Sept. 2 



to 

 Oct. 7 



f ^^ 



517 



5.0 



The percentages of twice-wintering larvse in Table XIX represent 

 only records of early observations when a nuraber of larvse had not 

 yet been hatched. It is of interest to note that the percentage of 

 2-year-old larvse was largest in vineyards located on the hill, owing 

 to the prevailing shorter season on the hill as cornpared with the 

 season in the valley. The time of transformation of the insects in 

 other stages has similarly been affected by the climatic conditions of 

 the past three years. 



In Table XX is shown the relative number of maturing insects and 

 twice-wintering larvse which were reared from eggs deposited at 

 known dates in 1908. 



Table XX. — The relative occurrence of transforming and twice-wintering larvse of the 

 grape root-worm reared from eggs laid in cages in 1908, at North East, Pa. 



Date of hatching 

 1908. 



Number of 



beetles 

 emerging, 



Number of 

 larvse win- 

 tering, 1909. 



July 16 



5 

 12 



9 







12 

 

 

 3 



July 20 



July 25 . . 



July 28 



Total 



19 



15 





In the rearing experiments other factors beside climatic conditions 

 have influenced the results and no direct conclusion should be drawn 

 from these observations beyond the point of establishing the fact that 

 under unfavorable conditions individual insects of this species do 

 remain two years in the ground before maturing. 



REARING AND EXPERIMENTAL METHODS. 



The underground habits of the larvse of the grape root-worm have 

 made the rearing of this insect comparatively difficult, and certain 

 obstacles have been overcome only by persistent and continued 

 experimenting. The rearing work in most cases has been planned 



