134 



Journal of Agricultural Research 



Vol. VI, No. 3 



than those on sandy land. This may have caused the difference in the 

 percentage of injury. However, only one suspected larva (a cutworm) 

 was found in the two fields. 



The different lepidopterous larvae noted were all observed to be feeding 

 upon the leaves. The tussock larvae were much the more abundant and 

 evidently produced a great deal of the injury. During the earlier exami- 

 nations nearly all of these tussock larvae were quite small. The injury 

 produced varied somewhat with the size of the larva. The very small 

 individuals fed only upon the epithelium of the lower side of the leaf and 

 the injury was not visible from above. With a slight increase in size 

 the larvae started to feed through the leaf and at this stage produced the 

 peculiar type of injury shown in Plate XIII, figure 2. I^ater the older 

 larvae (one-half to full grown) ate large holes in the leaves, and the injury 

 could no longer be distinguished from that of the other species concerned. 

 Plate XIII, figure 3, shows the injury produced by one nearly full-grown 

 tussock larva when confined in a large screen cage with cotton seedlings 

 growing in a pot. 



About May i nearly all cotton fields under observation suddenly began 

 to show, greatly increased injury until within a few days many fields had 

 practically every plant more or less mutilated. This proved to be due 

 to an invasion of grasshopper nymphs. These speedily became very 

 abundant and swarmed over the young cotton, feeding principally upon 

 the leaves. This is shown in Plates XIV and XV. These cotton leaves 

 were collected in the field when the young grasshoppers were feeding 

 upon them. 



A little later in May the 12-spotted cucumber beetle, or adult of the 

 southern corn rootworm (Diabrotica 12-punctata Olivier) , became abundant 

 locally and added to the injury. The work of these beetles closely 

 resembled that of the worms and grasshoppers, though the holes made 

 were usually not very large. At this' same time woolly-bear larvae began 

 to appear in the fields and produced the same injury. 



Following this great increase in injury to the plants caused by the 

 grasshoppers, counts were made to determine the percentage of injured 

 seedlings in four average fields near Tallulah. The information secured 

 from these examinations is shown in Table III. 



Table III. — Abundance of injured cotton seedlings after the grasshopper invasion 



May 14. 

 IS- 

 17- 

 17- 



Number of 

 seedlings 

 examined. 



800 



3>5oo 

 2, 000 

 I, 000 



Total 



Weighted average. 



7.300 



Number of 



seedlings 



injured. 



792 

 3,446 

 I, 920 

 I, 000 



7,158 



Percentage, 

 injured. 



99.0 



98.5 



96. o 



100. o 



98.0 



