ORIGIN AND DISTRIBUTION. 



on the veins, but except on the veins themselves the indications of 

 their feeding disappear in the fermentation proa 

 The work of the pesl should not be confused with 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 affected to any 

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

 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, 

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

 from si to 50 cent-, 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 .-hade was damaged to such an extent by white vein- 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 1906. Early tobacco was especially 

 affected by white vein^ in 1005. the injury having taken place pre- 

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

 a- containing 33 per cent of affected wrapper.-, practically one-half 

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

 crop i- 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 the period and amount of 

 rainfall. 



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

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

 throughout all the fields of shade tobacco. 



ORIGIN AND DISTRIBUTION. 



A- soon as possible after reaching Quincy, specimens of the tobacco 

 thrips were collected and sent to Dr. W. E. Hind-, an authority on 

 tin- group of insects. He found that they represented a new species 

 and has named and described them. 



Tin- insect was taken by the writer at Nacogdoches, Tex., on -hade 

 tobacco, as well a- at Quincy, Fla. In April adult- and larva 4 were 

 taken in large number- on cocklebur (Xanthium glabratum) growing 

 in the shade field- and in -mailer number- on dewberry, mustard, and 

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



■ Proc. Biol. Soc. Washington, Vol. XVIII, pp. 197-199, September, 19 



