52 MISCELLANEOUS KESULTS OF WOEK OF BUREAU- — IX. 



served, no larvae hatched until 19 days after the female was placed on 

 a plant. This insect was about 1 day from the pupa when placed 

 on the plant. Another female was observed for 4 weeks, when she 

 disappeared, quite probably dying of old age. Probably this thrips 

 lays from 10 to 20 eggs during her lifetime. The writer observed 10 

 larvEe on 1 plant with a single adult, and possibly some were killed by 

 mites, etc. 



Generations. — In greenhouses this insect is active during the entire 

 year, so that the number of generations is quite large. Taking the 

 maximum life cycle, this thrips might produce as many as 12 genera- 

 tions a year, provided that the species breeds continuously and con- 

 ditions are favorable to rapid growth. 



NATURAL CONTROL. 



Rain. — In its native home this thrips is probably kept under con- 

 trol by frequent rains. At Miami, Fla., where hundreds of crotons 

 are planted on hotel and private grounds, the author could find 

 no traces of injury and collected only 1 adult. Crotons that were 

 badly infested by this insect, kept in a greenhouse at Orlando, Fla., 

 during the winter of 1907, were placed outside in June and by the end 

 of the summer it was almost impossible to find specimens of the thrips 

 on them. In times of drought this insect may increase in such num- 

 bers as to cause serious injury where it occurs in the open. 



Natural enemies.— YveqneniXy a mite is found on plants infested 

 with the greenhouse thrips. On a few occasions the author has found 

 thrips with one of these mites fastened to its dorsum. Specimens of 

 this predaceous enemy were determined by Mr. Nathan Banks as 

 Lselaps macropilis Bks. 



ARTIFICIAL CONTROL. 

 EXPERIMENTS WITH REMEDIES. 



FUMIGATION EXPERIMENTS. 



A series of fumigation experiments was conducted against this 

 insect in its occurrence on croton at Orlando, Fla. All were made in 

 a small, fairly tight room, containing 660 cubic feet. 



Experiment No. 1. — April 27, 1908, at 4 p. m., a plant was fumi- 

 gated all night with one sheet of nico fume. It was a cloudy, cool 

 day, just after a rain, and a good breeze was blowing. On opening 

 the room at 8.15 a. m. there was quite a pronounced odor of nicotine. 



April 28, the paper below the plant was covered with this insect in 

 all stages, and many were also found on the plant. 



