36 BULLETIN 918, U. S. DEPARTMENT OF AGRICULTURE. 



been accumulated along this line, due to the nocturnal habits of the 

 moth and the fact that in Mexico it was so generally distributed that 

 no uninfested isolated fields were found. 



The average duration of the moth stage in captivity is about 14 

 days. If the moth flies only a short distance before coming to. a rest, 

 it would appear certain that it may again proceed for another short 

 distance. If there were nothing to influence the direction of its 

 flight, it might fly in any direction and as likely as not return to its 

 original starting point; but if the direction of the flight is influenced 

 by the wind, as it was in our observations, it would fly with the wind, 

 and where there is a prevailing wind from one direction the moth 

 would be carried in the same general direction farther and farther 

 from its starting point and might cover a considerable distance 

 before dying. In the eradication work in Texas a 5-mile non- 

 cotton zone around infested territory is used to prevent dispersal 

 by flight, and it is thought this zone is reasonably safe. The moths 

 have seclusive habits, and frequently hide in cracks, crevices, and 

 dark corners. At the railroad stations in the Laguna cars stand 

 upon the side tracks within a few yards of the cotton fields for days 

 or even weeks at a time while being loaded and unloaded. Trains stop 

 for long periods of time near the fields to unload supplies, and when 

 these stops are made at night, when the moths are flying about, it is 

 possible that some of the moths might secrete themselves in the cars 

 and later be carried to distant points. There is the same danger, though 

 to a lesser degree, in vehicles passing cotton fields along the roads. 



CARRIAGE OF LARVAE BY WATER. 



Cotton plants with bolls attached were often seen floating down 

 the Rio Nazas when it was at flood stage, and old bolls are carried long 

 distances when fields are overflowed. Some experiments were made 

 at Dr. W. D. Hunter's suggestion to determine how long larvae could 

 survive exposure to water. Free larva? with no protection whatever 

 pupated and produced moths after being in water in tubes for 44 hours. 

 Larvae survived for several days after being in water longer, but 

 none produced moths. Larvae in cocoons survived 72 hours in water 

 in tubes and free larvae placed in pill boxes perforated with a needle 

 produced one adult after 8 days' submergence in a pitcher. Pupae 

 did not survive as long as larvae. Old bolls picked in January, 1918, 

 and stored in the laboratory till April, 1919, were submerged in 

 water and left floating on the surface of water in a trough. Larvae 

 pupated and produced adults after 7 days in both instances, but no 

 adults emerged after 11 days in either case. 



Several plants containing green bolls heavily infested were placed 

 in the river and tied so that they could not float away. When there 

 was enough current in the river to keep the plants floating at the 

 end of the string the bolls were all washed away at the end of 4 to 5 

 days. When there was no current the plants sank to the bottom 

 and all the larva? were found dead in 3 days. It is quite likely, however, 



