UNITED STATES DEPARTMENT OF AGRICULTURE 



BULLETIN No. 416 ,, 



'S^T^i^u 



Contribution from the Bureau of Entomology 

 L. O. HOWARD, Chief 



■S^^^iJ-U 



Washington, D. C. 



PROFESSIONAL PAPER. 



January 29, 1917 



THE RED SPIDER ON COTTON. 



By E. A. McGregor and F. L. McDonough, 

 Scientific Assistants, Southern Field Crop Insect Investigations. 



CONTENTS. 



Page. 



Zonal distribution in the Southeast 2 



Classification and synon\Tny 3 



Food plants 4 



Life-history summary 5 



Description and habits 6 



Nature and extent of damage to cotton in 



the South 20 



fenerations of the red spider 21 



Page. 



Seasonal history 23 



Dispersion 27 



Climatic control 33 



Insect enemies of the red spider 34 



Apical swarming 58 



Remedial measures 59 



Summary and recommendations 67 



Bibliography 69 



The common red spider, Tetranychus himaculatus Harvey, is very 

 generally distributed in the United States. The map (fig. 1), which 

 •contains 297 records of occurrence in 34 States, shows the distribution 

 of the majority of reported cases. 



The species first became conspicuous as a pest to cultivated crops 

 in New England and the Northeast. The early complaints related 

 largely to greenhouse and dooryard plants, and it was not until 1855 

 that Glover reported some injury to cotton by the pest. As settle- 

 ment moved westward, records of occurrence from the Middle West 

 and, finally, the Pacific Slope, appeared in our literature. With the 

 exception of an outbreak in Louisiana, reported by Prof. H. A. 

 Morgan in 1893, severe occurrence of the red spider on cotton had 

 not been reported until 1903, at which time complaints of damage 

 came from South Carolina and Georgia. In 1904 Mr. E. S. G. Titus 

 (1905, a, h), then of this bureau, found severe infestation in fields 

 about Batesburg, S. C, and the following year he reported severe 

 injury in North Carohna, South Carolina, Georgia, and Alabama. 

 Since then the additional records of Dr. F. H. Chittenden and 

 Messrs. G. P. WrUUm, D. T. Fullaway, E. L. Worsham, H. F. Wilson, 



SrrTE. — This bulletin is of interest to thf«e who are subjected to loss or annoyance by the re'l spider. 

 .54.Wl°-ntill. 4KI— 17 1 



