158 APPLIED ENTOMOLOGY 



and fruit where they remain until the midsummer hardening of these 

 parts leads most of them to leave for various other food plants, until 

 August and September when they return to the citrus trees again and 

 lay their eggs in the leaves and stems of the plant. These winter over 

 and hatch the following spring. Following the production of adults 

 from the hatching and development of these eggs, there may be six to 

 eight generations during the season and all stages may be present at 

 once on a tree as late as December, though these die with colder weather, 

 leaving only the eggs to hatch in the spring. The last stage before the 

 adult, during which the insect is quiet, is passed in crevices of the trunks 

 or in rubbish under the trees, but not in the ground. 



Control. — Spraying, either with lime-sulfur wash using 1 part (if of 

 a density of 33°B4.) in 50 parts of water, or with more water than this if 

 the wash reads higher; or with Nicotine sulfate 40 per cent, at the rate 

 of 1 part in 800 parts of water, have given excellent results. The first 

 application should be made as soon as four-fifths or more of the blossoms 

 have fallen, and a second 10 days to 2 weeks later. If these two treat- 

 ments have been well-timed and thorough, the third can be delayed until 

 about 3 weeks after the second. A fourth treatment late in August or 

 early in September, if the returning insects are very abundant on new 

 shoots, will aid much in checking their increase. In all treatments the 

 application should be very thorough and with a pressure of at least 1251b. 

 Particular attention should be given at the second application to 

 completely drenching the fruit and any tender leaves. 



In addition to the species of Thrips given separate consideration 

 above, nu nerous other species are frequently of some importance. 

 Among these the Grass Thrips which sucks the sap from the stems of the 

 lighter grasses, turning them white and killing them, thus causing "silver 

 top" as it is called; the Greenhouse Thrips which attacks tomatoes, 

 cucumbers and many other plants in greenhouses in the North and out- 

 of-doors in the South, and the Camphor Thrips which is a serious pest 

 of the Camphor tree in Florida, are perhaps the most important. 



