12 



BULLETIN 



ACTIVITIES OF THE LARVAE. 



The young larvae begin to feed on the grape berry before they are 

 free from the eggshell and within a few minutes after emergence from 

 the shell burrow out of sight within the pulp. On the second or third 

 day they attack the seed and on the fourth day practically all the 

 larvae are located within the seed cavity of the grape berry. Later 

 they leave the seed cavity and continue to feed on the pulp, soon 

 converting the interior of the grape into a discolored mixture of pulp 

 and excrement. (PL II, E) 



Larvae reached full growth and issued from the grapes in from 13 

 to 25 days after the deposition of the eggs. Table IV shows the num- 

 ber that appeared on each day. 



Table IV. — Number of days elapsing from deposition of eggs by the grape curculio to 

 issuance of larvse from the grapes. 



Number of days in 



grape 



Number of larvae 

 issuing 



13 



14 



15 



16 



17 



18 



19 



20 



21 



22 



23 



24 



25 



2 



5 



51 



71 



29 



37 



17 



10 



11 



7 



1 



3 



3 



According to Table IV, allowing 6 days for the eggs to hatch, the 

 larvae remain in the grapes from 7 to 19 days, the average time being 

 from 10 to 12 days. 



The larvae squeeze through small holes which they make in the skin 

 of the grape berry and seek at once for places in which to pupate. 

 Most of the larvae leave the grapes during the morning hours, although 

 a few continue to appear during the afternoon. On August 4, 1917, 

 57 larvae dropped from a basket of infested grapes suspended in the 

 vineyard over a container. At the end of every hour the larvae in 

 the container were collected and counted. The results are shown in 

 Table V. 



Table V. — Time of day in which larvae of the grape curculio leave grape berries. 



[Standard time.] 



A. M. 



P.M. 



P. M. to A. M. 



Hours of day 



Number of larvse. . 



4-5 5-6 

 0, 2 



6^7 7-8 

 7 17 



8-9 9-1010-11 11-12 



13 5 21 5 



12-1 

 5 



1-2 



1 



2-4 

 



Table V indicates that more than one-half of the larvae leave the 

 grapes to pupate between the hours of 7 and 9 in the morning. Most 

 of the cocoons are constructed on the surface of the ground except 

 in cases where the larvae follow cracks or other openings into the soil. 

 They are frequently placed under faUen leaves or other small objects 

 and are sometimes attached to straws or stones lying on the surface 

 of the ground. 



