XATCKAL CONTROL. 13 



cabbage, and cauliflower. It may be distinguished from the tob 

 thrips by it- color, which is yellowish. 



Anthothrips niger Osborn is another species which was very abun- 

 dant at Quincy the summer of 1005. In oats and wheat bordering 



the tobacco field- it was found breeding in vast numbers with the 

 wheat and tobacco thrips. It was also occasionally taken on tobacco 

 and tomato. It is a strong flyer, and may be further distinguis 

 from the tobacco thrips by its much larger size and black color. 



A few specimens of AZolotkrips bieolor Hind- were taken on oats 

 and wheat in the vicinity of tobacco fields. This may be 



distinguished by the white or yellowish pigmentation of the first 

 throe -egments of the abdomen. 



Chirothrips cra88us Hinds was taken in October and November in 

 large numbers in the sheaths of grass growing in tobacco fields. It 

 was at first mi-taken for the tobacco pest, because of the similarity 

 in color, but may be easily distinguished, as it does not have the 

 jumping habit of the tobacco thrips. 



NATURAL CONTROL. 



Ranis. — Of the natural checks, rain is the most important. It is 

 known that nearly all thrips thrive during warm and dry weather, 

 and that they are washed from their food plant- and destroyed in 

 numbers by rain. This is true of the tobacco thrips in that it is 

 washed off by heavy rains, yet unle.-s the rain continues for several 

 day- few -«Hin to be destroyed, for at the end of the first or by the 

 second clear day following the writer ha- found it on the leave- in as 

 large numbers a- ever. 



The influence of rain upon the pest, however, was very noticeable in 

 its effect during the summer of 1!»(T). Up to the latter part of June 

 very little rain had fallen, and the drought was showing it- effect on 

 the unirrigated fields. At this time the dry spell was broken and 

 rain- were heavy and frequent. The June. 1905, rainfall, which was 

 nearly three times that of the preceding June yet -till below the nor- 

 mal, nearly all fell during the latter part of the month and was fol- 

 lowed by the heavy July rainfall, which was the greatest since I 

 and more than twice that of 1004. A- a result the thrips were kept off 

 the leaves, the plant- grew rapidly, and priming was forced into 

 twenty days where it usually take- thirty. The -and leave- were lost 

 in large part because of tin- rapid ripening and the leaves affected to 

 the greatest extent by white vein were thus eliminated from the crop. 

 A- the result of these weather conditions, white vein- in the Ian 

 bacco were reduced to a very -mall percentage. 



The great amount of injury in 1904 was undoubtedly due to the 

 exceptionally droughty season. This will be shown by tin 1 accom- 

 panying chart dig. 2) of total monthly precipitation for the last 

 seven year-. That during L905 and 1906 the Injury was -o much 



