THE EED SPIDER ON COTTON. 35 



Chittenden (1909) observed larvse of Scymnus punctum, Cecidomyia 

 cocddarum, (Jhrysopa rufilabris, and all stages of Thrips sexmaculatus 

 to be predatory on red spiders on the Kentucky coffee tree {Gymno- 

 cladus dioica) at Washington, D. C, dm^ing July and August, 1906. 

 He states that the Scymnus larvae were the most effective. In Colo- 

 rado, Weldon (1909) found lacewing-fly larv^ and Scymnus punc- 

 tum to be the principal enemies of the red spider. Worsham (1910) 

 states that the only natm'al enemy observed during the studies in 

 Georgia was Stethorus punctum, which fed, both in the larval and 

 adult forms, on the mites and the eggs. It was Quayle (1913) who 

 first gave us a considerable list of red-spider enemies. He does not, 

 however, differentiate between the predators of T. mytilaspidis, T. 

 sexmaculatus, and T. himaculatus. He states that most of the obser- 

 vations were made on the citrus mite. Parker's investigations (1913) 

 in central Cahfornia during 1911 and 1912 revealed the presence of 

 the following predators, which he states he has seen preying upon 

 red spiders: TripJdeps tristicolor (nymph and adult), Scymnus nanus, 

 Scymnus marginicoUis, Pentilia sp., and Chrysopa calif ornica. The 

 lacewing-fly larvae were most active. Finally, Ewing (1914) lists the 

 following species as actively predatory on the red spider in Oregon: 

 the mite Seius pomi, TripMeps insidiosus, syrphus-fly larvae, and 

 Stethorus punctum. Other species of mites and insects are men- 

 tioned by Ewing either as having been reported elsewhere on the 

 Pacific Coast or as being probable enemies. Ewing estimates Seius 

 to be the most valuable red-spider enemy in Oregon. All told, these 

 enemies of the common red spider make a total of a dozen species 

 which, to date, have been reported as definitely feeding upon Tetra- 

 nycJius himaculatus. Neither Parker nor Ewing appears to believe 

 that substantial control accrues from the activities of the red-spider 

 enemies. 



In the case of each of the seasons 1911, 1912, 1913, and 1914, 

 during which the red spider has been under observation at Bates- 

 burg, S. C, a sudden decimation of a more or less complete nature 

 has occurred. Figure 8, page 26, presents a diagram which consists of a 

 composite curve representing the average seasonal status of the red 

 spider in South Carolina for 4 years. The low summer point, reached 

 in July, indicat<!s graphically the combined control value of predatory 

 species. The red spider at the pr(?sent tim(i is known to be the 

 host of 31 species of artlu'opod enemies. Of these, 5 are mites 

 (Acarina), 3 are thrips (Thysanoptcra), 4 are bugs (Hemiptera), 4 

 arf. lacewing fli<;s (Neuroptera), 2 ai-e midges (Diptera), 4 are s3Tphid 

 i\'u'H (DipU'T'd), 8 are lady-lxictk^s (Cohsoptera), and 1 is a noctuid 

 moth (Lopidoptera). Th(!se predators, in turn, are known to be 

 attax^kcid by 75 sp(;cies of predators and parasites. 



