Circular No. 151. issued July 15, 1912. 



United States Department of Agriculture, 



BUREAU OF ENTOMOLOGY. 



L. O. HOWARD, Entomologist and Chief of Bureau. 



THE GREENHOUSE THRIPS/ 



{Heliothrips haimorrhoidalis Bouche.) 



By H. M. Russell, 



Entomological Assistant. 



INTRODUCTION. 



The greenhouse thrips has been the cause of considerable injury to 

 ornamentals during the past century, and where its presence is not 

 suspected or treatment is neglected it will cause the utter ruin of cer- 

 tain plants, in the greenhouse, grown principally for the beauty of 

 their foliage. Likewise in the more tropical sections of the United 

 States, such as southern Florida and southern California, this insect 

 causes great damage to some outdoor plants. 



DESCRIPTION AND LIFE HISTORY, 



The adult of this thrips is a small, active insect about one twenty- 

 fourth of an inch in length and dark brown in color, \vith the tip of the 

 body decidedly lighter. The appearance of this insect is sufficiently 

 illustrated in figure 1 to render a more detailed description unneces- 

 sar}^ This insect feeds on the foliage of the plant attacked and 

 removes all the coloring matter, leaving the leaf white and, in severe 

 cases of attack, dead. During this period the female deposits her eggs 

 (fig. 2, a) within the leaf tissue and these hatch in the greenhouse in 

 about eight days. The larva which hatches from the egg is a minute 

 white insect of the shape indicated in figure 2, h and c. During this 

 period, which requires from 10 to 20 days, varying with the tempera- 

 ture, the larvas feed together in colonies on the surface of the leaf and 

 remove the coloring matter in the same manner as do the adults. While 

 engaged in feeding, the larva exudes a large drop of reddish fluid from 



1 For a fuller teelmioal treatment of this insect see "The Greenhouse Thrips," Bui. 64, Pt. VI, Bur. Ent., 

 U. S. Dept. Agr. 



42051°— Cir. 151—12 X 



