35 



of the weather. It in ahiiost certain that these minute insects are not 

 active during rainy weather, as they could scarcely live under such 

 conditions. It is further probable that they are actually destroyed in 

 large numbers b}^ the rain, despite their efforts to secure safe retreat. 



As opposed to the favorable influence of rain}^ weather on the boll- 

 worm by interference with the work of its natural checks must be 

 mentioned the considerable destruction of eggs under the same condi- 

 tions which are favorable to its increase in other stages. A heavy rain 

 has the effect of washing from the plants to which they are attached 

 many of the eggs, the great majority of which are destroyed by the 

 combined mechanical effects of the rain and particles of soil. Fre- 

 quent observations before and immediately after heavy rains leave no 

 doubt that many eggs are thus destroyed. 



The foregoing remarks have been confined to an explanation of 

 some of the factors involved in the greater destructiveness of boll- 

 worms to cotton following rain}^ weather in late July and in August. 

 The month of August, including during some seasons the last week or 

 ten days of Jul}^, marks the period of danger from bollworms. The 

 tendency on the part of the planters has been therefore to limit the 

 influence of weather conditions to about this period. The insect, how- 

 ever, is subject to these same conditions in its several generations 

 from early in the spring until late in the fall, and during the winter 

 the pupae in the ground are probably much influenced by climatic con- 

 ditions. The possibility of severe injury to cotton in July and August 

 therefore depends also on how they have been able to maintain their 

 numbers during the balance of the year. Owing to their rate of mul- 

 tiplying in geometrical progression, the destruction of a pupa during 

 the winter, or of a larva in young field corn in the spring, would 

 diminish the possible number of bollworms ready to attack cotton in 

 August by many thousands. Their abundance or scarcity on cotton 

 is therefore seen to depend on other conditions than those existing 

 during the immediate period of injury. 



INJURY TO COTTON FROM OTHER CAUSES THAN THE BOLL WORM. 



The known capabilities of the boll worm to injure cotton has led to 

 its being charged with practically all forms of injury affecting the 

 squares and bolls, aside from that done by the boll weevil, and the 

 seriousness of its ravages has thus often been greatly exaggerated, 

 especially by those not accustomed to examine closely into matters of 

 this kind. As is shown on a later page, there are a few insects affect- 

 ing both corn and cotton which might, from the character of their 

 work, be mistaken for bollworms. These are, however, relatively 

 unimportant in the extent of damage. Certain hemipterous insects, as 

 Calcori^ rajyidus Sa}^, Honialodisca triqiietra Fab., and Largus ductus 



