BULLETIN No. 179. 



DEPARTMENT OF ENTOMOLOGY. 



THE GREENHOUSE RED SPIDER ATTACKING 



CUCUMBERS AND METHODS FOR 



ITS CONTROL. 



(Tetranychus bimaculatus Harvey.) (Class, Arachnida; Order, Acarina; 

 Family, Tetranychidcc.) 



BY STUART C. VINAL. 



INTRODUCTION. 



The minute spimaing mites, commonly called red spiders, have long 

 been known as among the most troublesome of greenhouse pests, although 

 they also cause a great deal of damage to flowers, vegetables and trees 

 growing out of doors. A greenhouse affords an almost ideal environment 

 for the development and rapid multiplication of red spiders, and as a 

 consequence we find this pest taking advantage of the opportunity offered 

 and doing great damage to many of the principal crops grown in green- 

 houses. 



The production of vegetables under glass is an expensive process, in- 

 volving a large investment of capital and a continual expense- to maintain 

 such an establishment. To counterbalance this expense the value of the 

 crop must be proportionally high, and anything which interferes with 

 the fullest development of the plants reduces the profits materially. 



Without doubt the common red spider {Tetranychus bimacidatus 

 Harvey) is the most widely distributed and destructive pest of green- 

 house cucumbers. Nowhere in America is the cucumber forcing industry 

 more highly developed than in the market-garden district of Boston, 

 Mass., and therefore the injury caused by this pest assumes its greatest 

 economic importance in this section. 



During the last few years numerous inquiries have been received by 

 the Massachusetts Experiment Station from market gardeners in regard 

 to the control of red spiders attacking greenhouse cucumbers. Because 

 of the lack of an efficient method of control very few recommendations 



