THE SUGAR-BEET THEIPS. 3 



yellow calla (Richardea aethiopica), tomato (Lycopersicum), and 

 grape (\^itis). 



Tlie writer has also foimd it on Begonia, spinach (Spinacia), sweet 

 potato {Ipomoea Jatotos), strmg beans (Phaseolus), and Mexican tea 

 {Chenopodium arnbrosioides) . 



EXTENT AND NATURE OF INJURY. 



The injury caused by the sugar-beet thrips is similar to that of the 

 other species of thrips of the group. The plant is attacked by the 

 adult and nymphs in the same manner. The leaf cells are pierced, 

 and the plant juices withdrawn, causing the cells to shrivel and turn 

 white. When a number of these cells are destroyed they appear as 

 irregular white or light-brown spots. If the attack is severe, the 

 whole leaf surface becomes invested by these spots and finally shrivels 

 and dries. The nymphs also render the plant unsightly through the 

 brown watery excretion from the aUmentary tract, which discolors 

 the leaves. 



Plate I shows a leaf of Swiss chard attacked by this thrips. 



HABITS OF NYMPHS OF FIRST AND SECOND STAGES. 



^Mien ready to emerge, the young nymph breaks through the thin 

 eggshell and pushes its way upward until all but the last abdominal 

 segment is free. It remains upright and supported by the last seg- 

 ment until the appendages which are folded beneath the body unfold 

 and become sufiiciently hard for use. The forelegs are the first to 

 unfold, followed by the middle and hind pair. The antennae are now 

 brought forward. The nymph then places its legs on the surface of 

 the leaf and by constant pulling frees the body. A period of from 

 20 to 25 minutes is required for complete emergence. 



The newly-hatched nymphs crawl about for a short time before 

 commencing to feed. They usually collect and feed in colonies on 

 the underside of the leaf, but if food is not abundant, both sides are 

 attacked. ^Shortly after feeding, the body becomes discolored by the 

 ingested food. Th(i watery excretion from the ahmentary, tract is 

 collected as a globule, which extends over the entire body except the 

 h(iad, and increases in size until it becomes too large to carry. It 

 is then dropped and spreads over the leaf, giving it an unsightly 

 appearance. The older nymphs are very active and when disturbed 

 move rapidly, with the tip of the abdomen extended upward. 



Wlien full grown, tlie nymph s(Hiks a secluded spot in which to 

 transform. The curled portions of dead leaves form a favorite place 

 of concealment, altliougli the base of the plant and the portion of the 

 leaves along the midribs may be scLjcted, 



