ORIGIN AND DTSTHiBUTION. 7 



on the veins, but exeej)t on the veins themselves the indications of 

 their feeding disappear in the fermentation process. 



The work of the pest slioukl not be confused witli the so-called 

 '' white vein " that sometimes occurs in tobacco grown in the North 

 and which seems to be due to a physiological disorder of the plant. 



As a result of the thrips's work, when the crop is alfected to any 

 extent, all the white- vein tobacco must be sorted into a grade by itself 

 and sold as such, the expense of grading being thereby largely in- 

 creased. The value of the crop also is greatly reduced, as there is no 

 demand for this grade at present. There seems to be quite a variation 

 in the estimates of the depreciation of tobacco thus affected, one 

 packer estimating the value as decreased from $1.50 to 30 cents, or 

 a loss of $1.20 per pound, while another packer places the decrease at 

 from $1 to 50 cents, or a loss of 50 cents per pound. These seem to 

 be maximum and minimum estimates. 



For the year 1904 it is estimated that 20 per cent of the crop grown 

 under slat shade was damaged to such an extent by white veins that it 

 was thrown into a grade by itself. 



The injury for 1905 was decreased to a great extent by the heavy 

 rainfall in the latter part of June and in July. In the crop of tobacco 

 sprayed with emulsion there were practically no white veins to be 

 found, and this was the case in 190G. Early tobacco was especially 

 affected by white veins in 1905, the injury having taken place pre- 

 viously to the rains. One crop of tobacco is estimated by the planter 

 as containing 33 per cent of affected wrappers, practically one-half 

 of which must necessarily be placed in a separate grade. Another 

 crop is estimated as containing 20 per cent of affected wrappers, 10 

 per cent being placed in a separate grade. The amount of injury will 

 vary from year to year, depending upon tlie period and amount of 

 rainfall. 



In the past the greatest damage has been to that particidar section 

 near the original shade, but the thrips now seem to bo disseminated 

 throughout all the fields of shade tobacco. 



ORIGIN AND DISTRIBUTION. 



As soon as possible after reaching Quincy. specimens of the tobacco 

 thrips were collected and sent to Dr. ^V. E. Hinds, an authority on 

 this group of insects. He found that they represented a ucav species 

 and has named and described them." 



This insect was taken by the writer at Nacogdoches, Tex., on shade 

 tobacco, as well as at Quincy, Fla. In April adults and larva» were 

 taken in large numbers on cocklebur {Xanthiinn f/hibratum) growing 

 in the shade fields and in smaller numbers on dewberry, mustard, and 

 shepherd's purse blossoms. It has been taken by the writer at Dallas, 



a Proc. P.iol. Sue. Wiisliinixtoii. Vol. Will. pi.. 1!)7-1!»!). St'pti'inbor, 15K)5. 



