U. S. D. A., B. E. Bui. 109, Part II. T. C. & S. P. 1. 1... November 11, 1911. 



PAPERS ON INSECTS AFFECTING YEGETABLES. 



THE SOUTHERN BEET WEBWORM. 



(Pachyzancla bipunctalis Fab.) 



By F. H. Chittenden, Sc. D., 

 In Charge of Truck Crop and Stored Product Insect Investigations. 



INJURIOUS OCCURRENCES AND NOTES ON HABITS. 



On September 24, 1906, the Bureau of Entomology obtained from 

 Mr. F. W. Roeding, Wichita Falls, Tex., the larvae, pupae, and adults 

 of the pyralid moth Pachyzancla bipunctalis Fab., which had been 

 found operating on foliage of table beets in that vicinity. One larva 

 transformed to pupa on September 25, and the adult issued October 

 3, the pupal period thus having occupied eight days in an average tem- 

 perature of about 70° F. From this lot imagos continued to issue 

 until October 2, and a larva matured October 10 which would have 

 produced an imago about October 30. 



During October, 1907, Mr. H. M. Russell observed larvae at Dade 

 City, Fla., on beet tops from 6 to 8 inches high, u webbing up" the 

 leaves with the edges of the leaves folded together or joining two or 

 more leaves to make a nest in which to hide. From this conceal- 

 ment they emerge and eat the leaf cells composing it, usually 

 leaving the leaf skeletonized or very thin. In these nest-forming 

 and leaf-eating habits the insect resembles the related Pyraustidae. 

 Mr. E. B. Embry, located at Dade City, Fla., stated that the larvae 

 of this species had injured the foliage of small beets so badly as to 

 reduce his crop about 50 per cent. As late in the season as November 

 29, the web worm larvae were found in another locality at Dade City, 

 some of which showed parasitism. In January, 1909, larvae were 

 observed attacking beets at Boynton, Fla., and in March, beets af 

 Miami, Fla. 



From webworm material obtained October 18, one pupated October 

 23, and the moth issued November 8. Another larva pupated 

 November 6 and the adult issued on November 21, thus indicating a 

 pupal period covering from 15 to 16 days, in the latitude of Washing- 

 ton, D. C. In another case the pupal stage lasted from December 31 

 to January 22, or a total period of 23 days. The temperature at 



Washington was moderately cold. 



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