42 



THE GRAPE ROOT-WORM. 



limited to a very short period (see ^g. 16). The first beetle in the 

 field was observed July 11. In the spring of 1908, on collecting 

 larvae in different vineyards two distinct sizes were found, as possibly 

 due to climatic conditions of previous seasons. The larger larvae 

 were full grown, while the smaller varied from one-third to three- 

 fourths grown. In the rearing cages the full grown larvae trans- 

 formed normally and without further feeding. Of the smaller larvae 

 few matured at the normal time, many were quite belated, while quite 

 a number wintered, thus spending two years as larvae in the ground. 

 As a result of the early season of 1908 the beetles commenced to 

 emerge by June 16. The emergence extended over a long period; 



JUNE 



/5 ZO 25 3 



JULY 



5 /O /5 ZO 25 d 



AUG. 



5 /O /6 















A 







llTfrrrrT 













rrrf^ 



i 



p'l 





ii 



Mirn 



^11 lliir 





















r 



A 



ii 



i 





w 



Im 



BTHir 











Fig. 16. 



-Diagram showing variation in time of emergence of beetles of the grape root-worm during 

 1907, 1908, and 1909 at North East, Pa. (Original. ) 



the latest beetles to emerge appeared in the rearing cages July 28. 

 This longer emergence period was partly due to the delay in the 

 development of larvae that hatched in 1907. In the spring of 1909 

 the larvae were again of a more uniform size as a result of the long 

 season of 1908, and the emergence in 1909, as recorded in figure 16, was 

 about normal. On examining larvae in the field in the early fall of 

 1909 data were obtained as to the prevailing number of 1-year and 

 2-year old larvae (Table XIX). At the dates of these observations 

 only a few of the new-brood larvae had attained one-half their growth 

 while many of the eggs had not yet hatched, and since the 1908 brood 

 larvae were full grown the two broods could then be readily told apart. 



