78 



NUMBER OF LARYJE ON A SINGLE PLANT. 



As before mentioned, a large number of young larvae may be present 

 in a single ear of corn, but of these never more than one, two, or less 

 frequently three mature. On cotton the number present on each 

 plant is so variable that records of this sort can have no permanent 

 value. The injury corresponds closely to the number of larvae, and 

 estimates are best made by noting the extent of the injury. 



RELATION TO THE NUMBER OF EGGS LAID. 



The most important fact to be noted is the wholesale destruction 

 which takes place among the young larvae. At times when nearly one 

 hundred eggs are present on a single ear of corn, and but two larvae 

 can mature, the elimination reaches 98 per cent. On cotton the num- 

 ber of eggs laid per plant is considerably less, and the proportion of 

 larvae to mature so much the greater. 



PERCENTAGE OF CORN PLANTS INFESTED. 



In the early part of the season, as has already been pointed out, 

 injury to corn by the first generation of larvae is not great, but increases 

 later with the appearance of the second brood. This is sho\vn in the 

 following table, compiled from observations of over 6,500 corn plants 

 made at Paris, Tex. : 



Table XXVIII. — Percentage of infestation in early corn. 



Date. 



Mav 1 

 May 13 

 May 24 

 May 24 

 May 24 

 May 24 

 May 31 

 May 31 

 June 16 

 Julv 13 

 July 20 

 July 20 

 July 20 

 July 21 

 Sept. 28 



Age of corn. 



18 to 24 inches . 



2ito3ifeet 



3 feet 



do 



4 to 6 feet, tasseling 

 3 to 4 feet, tasseling 

 3 to 5 feet, tasseling 



Silk and tassel 



Roasting ears 



do 



-do. 

 .do. 

 .do. 

 .do 



Number of 

 observa- 

 tions. 



1,000 

 650 



1,200 

 170 

 200 

 650 



1,000 



1,000 

 100 



80 

 100 

 157 

 180 



75 



Number 



of 



larvae. 



19 



"98' 

 116 



Number 



of 

 injuries. 



56 

 110 



176 



75 



Per cent 



of 

 injury. 



0.1 



0.9 



1.25 



1.2 



1.0 



3.0 



5.4 



1.4 



27.0 



98.0 



57.5 



56.0 



70.0 



97.2 



100.0 



A second table shows the percentage of infestation at a number of 

 other localities during the latter part of the season. It includes data 

 for localities representing practicall}^ the entire cotton belt, showing 

 an average percentage of infestation of 78.3. The difierence between 

 the early and late corn is plainly seen, averaging only 78 per cent for 

 a number of cases of the former and 98 per cent for the latter. 



