Thysanoplera 295 



Order thysanoptera 



REARING THRIPS TABACI* 



THE thrips were reared on successive plantings of onions in a green- 

 house. The thrips were transferred from the plants to vials by 

 sucking them into a glass tube which was about 4 inches long and about 

 Y 2 inch diameter. [See Fig. 41.] A cork was placed in one end of this 

 tube, through which a 2 -inch length of glass tubing % inch in diameter 

 was inserted. A 12 -inch piece of rubber tubing was inserted in the other 

 end of the large glass tube. A piece of silk placed over the end of the 

 rubber tube prevented the passage of thrips into it when they were being 

 sucked into the glass tube and also furnished a tight fit between the rub- 

 ber and the glass, thus preventing the escape of the thrips. The rubber 

 made the apparatus flexible so that it was easy to reach the thrips on 

 any part of the plant. When the desired number was secured, the cork 

 was removed and the thrips shaken into vials, from which they might 

 later be transferred to the feeding cages. 



The cage finally evolved for controlled feeding experiments was a 

 Syracuse watch glass and its cover. The inside of the bottom of the 

 glass was covered with white blotting paper, the edges of which were 

 sealed to the glass by means of hot paraffin to prevent the thrips being 

 caught between the paper and the glass. When the cage was inverted 

 the blotting paper absorbed the excess moisture, preventing con- 

 densation within the cage and the possible drowning of the thrips. 

 It also aided in maintaining a high humidity which seemed de- 

 sirable. Three discs of blotting paper the size of the coverslip, placed 

 one on top of the other, were used as feeders. The feeder was placed 

 on the cover of the watch glass, covered with a coverslip to keep the 

 thrips from sticking to the feeder, and then saturated with the substance 

 to be fed. The saturated feeder adhered fairly well to the cover of 

 the cage. After the thrips were shaken into the cage, the cover was 

 sealed to the watch glass by means of hot paraffin. This prevented the 

 escape of the thrips and aided in maintaining the humidity. The cage 

 was then placed cover downwards in the oven where a constant tempera- 

 ture of 21 C. was maintained. Even though the cage was placed in 

 an oven, the relative humidity remained high throughout the experiment 

 for condensation occurred between the blotting paper and the bottom 

 of the cage which it lined. The feeders were also damp when the cages 

 were opened at the end of the experiment. There seemed to be sufficient 



♦Abstracted from "The utilization of carbohydrates and proteins by onion thrips, 

 Thrips t abaci Lindeman," a thesis submitted to the faculty of Cornell University, Sep- 

 tember 1932, by Burl Alva Slocum, University of Nanking. 



