8 BULLETIN" 358, V. S. DEPARTMEXT OF AGEICULTUEE. 



The longevity records of 1914 and 1915 added to those previously 

 obtained show that 6,119 weevils fed on water averaged 9.9 days; 

 308 weevils fed on cotton averaged 8.6 days; 542 weevils fed on mal- 

 vaceous plants averaged 9 days; 146 weevils fed on cotton foliage 

 averaged 24.3 days and 534 weevils fed on cotton squares averaged 

 54.2 days. The most interesting features of the recent investigations 

 on longevity are the greater adaptability of grandis for abnormal food 

 plants and the ver}" great longevity of thurheriae on any food. In 

 view of this trend displayed by grandis and the adaptations which 

 have abeady been made by thurheriae it seems reasonable to expect 

 that grandis will continue to acquire greater hardihood when offered 

 only abnormal foods. 



Field cage studies. — For comparison with the laboratory tests of 

 longevity, several experiments were conducted m field cages. Large 

 cages covered with 16-mesh screen were placed over growing cotton 

 plants and the fii'st hibernated weevils found m the field in the spring 

 were placed in them. Six cages in all were started on dates ranging 

 from May 12 to June 19. These cages were watched for the cessation 

 of weevil injury to the plants. However, the greater part of the new 

 weevils died almost immediately after mstallation and the latest 

 date on which a weevil was observed alive was July 22 . It is apparent 

 that the conditions are very abnormal in these cages, owing to the 

 effect upon the Ught, temperature, humidity, etc. In fact, the plants 

 themselves make a very abnormal growth when caged. A few obser- 

 vations were made durmg this period to determine the difference in 

 temperature inside and outside these cages and they indicated a 

 slightly higher daily maximum inside the cage than outside. The 

 observations general!}' indicate that the conditions are very abnormal 

 in these cages and that there is serious danger of error in drawhig 

 conclusions based only on such observations. 



FOOD PLANTS OF THE WEEVIL. 



During the early hivestigations on the boll weevil many attempts 

 were made to find the weevils f eedmg or breedmg on any plant other 

 than cotton but they were uniformly unsuccessful. In fact, the fii'st 

 record of a cotton boll weevil feeding in nature on any plant other 

 than cotton was in 1913, when one individual was found at Victoria, 

 Tex., eatmg a bloom of Hibiscus syriacus. Observations smce that 

 time have shown a number of cases of the weevils feeding on plants 

 closely related to cotton. The most unportant of these seem to be 

 okra and the various wild species of Hibiscus. 



Ohra. — Okra is found very closely associated with cotton in many 

 parts of the cotton belt. In fact, the plants are usually scattered 

 through the cotton fields or are in the small garden patches adjoining 

 cotton. Conseqiiently there is a very good opportunity for the 

 weevils to attack this plant. 



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