116 



parasite are deposited inside the boll worm eggs b}^ the female, which 

 is provided with a sharp ovipositor capable of piercing the hard chiti- 

 nous shell of the egg. The young parasitic grubs eat out the contents 

 of the egg^ thus preventing hatching. 



The following tables, compiled from a large number of records, show 

 very graphicalh^ the large percentage of eggs which fail to hatch on 

 account of these parasites: 



Table XLV. — Percentages of parasitized eggs on corn, 1903. 



Date of exami- 

 nation. 



Number 

 of eggs 



ex- 

 amined. 



Locality. 



Eggs on— 



Per cent 

 para- 

 sitized. 



May 31 



194 

 100 

 144 

 283 

 747 

 100 



Victoria, Tex 





84 



June 1 



do 



Corn leaves 



72 



Do 



do 





83 





do 



Corn leaves 



70 



Do 



do . . ... 



. . do ... 



44 8 



Augusts 



Calvert, Tex 





26 









Table XLYI. — Percentages of eggs parasitlzeil, 1904- 



Date of exami- 

 nation. 



Number 

 of eggs 



ex- 

 amined. 



Locality. 



Plant. 



Per cent 



para- 

 sitized. 



May 16 



150 

 10 

 20 

 40 

 31 

 32 

 10 

 40 

 40 

 40 

 40 

 40 

 34 

 44 

 40 

 28 



Paris, Tex 





59.3 



June 3 



do 



do 



70 



June 10 



do 



do 



80 



August 1 



do 



do 



50 



August 12 



Do 



...do 



Corn silks . 



58 



do 





68.7 



Do 



. do 



Tobacco leaves 



30 



August 14 



August 16 



August 20 



Do 



do 





100 



do 



Cotton 



22 5 



do 





92.5 



do 



Corn silks 



62 5 



August 29 



do 



Corn leaves 



76 



September 3 



September 7 



September 24... 

 October 19 



do 



Cotton 



35.5 



do 



Tomato leaves 



86.5 



do 





82.5 



.do ... 



.do 



43 











Per cent. 



Observed average parasitized during 1903 63. 3 



Observed average parasitized during 1904 63. 4 



General average, all observations 63. 35 



Glancing down the table, it will be noted that the maximum parasi- 

 tization is on corn leaves, with corn silks next in susceptibility, and 

 parts of the cotton plant considerably in the rear. This may pos- 

 sibly be due to the hindrance offered to the locomotion of the Tricho- 

 gramma during the process of oviposition by plant hairs, since the 

 leaves of corn are more nearly free from these than the other objects 

 mentioned. 



The first appearance of Trichogramma in the spring corresponds 

 approximately with the first general occurrence of boll worm eggs on 



