THE GKEENHOUSE THRIPS. 



around the edges of the leaf. 

 In severe attacks the insects 

 spread to the upper surface of 

 the leaves, and in a short time 

 this as well as the underside is 

 nearly devoid of color. Both 

 sides become thickly covered 

 with minute drops of reddish 

 fluid voided by the thrips, 

 wliich gradually change to 

 black. As the attack con- 

 tinues, the leaves become limp 

 and yellow and eventually chop 

 off, so that the plants that are 

 not treated to prevent injury in 

 many cases lose their entire foli- 

 age. Figure 6 shows normal 

 croton and figure 7 croton to- 

 tally defoliated by the adults 

 of this insect. 



Tliis insect injures plants in 

 two ways : First, a serious drain 

 on the vitality of the plant is 

 produced by the feeding of thou- 

 sands of thrips, so that the 

 growth is seriously checked and 

 in neglected cases causes the 

 death of the plant. Second, it 

 destroys the beauty of the 

 plants for ornament by event- 

 ually despoiling them of their 

 foliage. 



In southern Florida tliis insect 

 attacks the mango and alligator 

 pear and causes great injury by 

 feeding on the foliage and it 

 may also cause injury by feed- 

 ing on the young fruit and scar- 

 ring it to a large extent. 



At Santa Barbara, Cal., tliis 

 insect occasionally becomes so 

 abundant on orange trees as to 

 ruin the fruit and cause the en- 

 tire foliage to drop. The guava 

 industry there has also suffered 

 severely from this insect. 



Fig. 7.— Croton plant totally defoliated by the green- 

 house thrips, Washington, D. C, February, 1012. 

 (Original.) 



