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BULLETIN 19, U. S. DEPARTMENT OF AGEICULTUEE. 



LENGTH OF EGG STAGE. 



Since we were unable to secure actual records of egg deposition 

 from which to make a starting point in order to determine accurately 

 the length of the egg stage, an approximation of this period was ob- 

 tained in the following manner: 



During the season of oviposition a number of adults were confined 

 in an air-tight globe cage (PI. II, fig. 1) upon the uninfested foliage 

 of a small grapevine possessing not more than three or four healthy 

 leaves. After 24 hours all the adults were removed. The vine was 

 protected from further infestation and after seven days had elapsed 

 was examined daily for the appearance of nymphs. A record was 

 made of the date of the first nymphs to appear. These were removed 

 from the cage and all other nymphs to hatch were removed at inter- 

 vals of 24 hours. In the experiments recorded below the adults were 

 placed on an inclosed grapevine, July 4, at 1 p. m. These adults were 

 removed July 5, at 1 p. m. The newly hatched nymphs were removed 

 on the dates recorded in Table I. 



Table I. — Length of incubation period of eggs of the grape leaf hopper. 



50 adults placed on vine July 4, 1 p. m.; adults removed 

 from vine July 5, 1 p. m. 



Date and hour of removal of newly 

 hatched nymphs. 



Number 

 of nymphs 

 removed. 



Incuba- 

 tion, 

 period. 



1912. 

 July 17, 1 p. m 



6 



46 



58 



7 



5 



Days. 



11 to 13 



12 to 14 



13 to 15 



14 to 16 



15 to 17 



July 18, 1 p. m 





Jul v 20, 1 p. m 





50 adults placed on vine June 25, 2 p. m.; adults removed 

 from vine June 26, 2 p. m. 



1912. 

 July 9, 2.30 p. m 



15 



45 



13 







1 



Days. 



11 to 13 



12 to 14 



13 to 15 



July 10, 2.30 p. m 



July 11, 2.30 p. m 



July 12, 2.30 p. m 



July 13, 2.30 p. m 



15 to 17 





100 adults placed on vine June 27, 2 p. m.; adults removed 

 from vine June 28, 2 p. m. 



1912. 

 July 12, 2 p. m 



14 



44 



19 



8 



1 



Days. 



13 to 15 



14 to 16 



15 to 17 



16 to 18 



17 to 19 



July 13, 2 p. m 



July 14, 2 p. m 





July 16, 2 p. m 



50 adults placed on vine July 27, 2 p. m.; adults removed 

 from vine July 28. 2 p. m. 



1912. 

 Aug. 20, 2 p. m 



15 

 4 

 11 



Days. 



22 to 24 



23 to 25 



24 to 26 





Aug. 22, 2 p. m 





50 adults placed on vine August 10, 2 p. m.; adults removed 

 from vine August 11, 2 p. m. 



1912. 



2 

 1 

 3 

 

 

 2 

 1 



Days. 



12 to 14 



13 to 15 



14 to 16 







Aug. 27, 2 p. m 



Aug. 28, 2p.m... 





Aug. 29, 2 p. m 



17 to 19 

 20 to 22 



Sept. 1, 2 p. m 



