DISEASES IN GREENHOUSE 131 



FIG. 20. GREENHOUSE ThripS, O EGG. h LARVA FIRST 

 STAGE. C LARVA FULL GROWN. (AFTER RUSSELL.) 



Besides the sweet pea, thrips feed on 

 lilies, azaleas, croton, dahlia, phlox, ver- 

 bena, pink, and ferns, and on a number of 

 other ornamentals, both in the greenhouse 

 and in the open. 



RED SPIDER 



Tetranchys bimaculatus Harv. 



Even more dangerous to sweet peas than 

 mites are Red Spiders (fig. 21), which at- 



