6 BULLETIN" 173, U. S. DEPARTMENT OF AGRICULTURE. 



in his report before the Royal Dublin Society for 1900, 1 and as the 

 "pear thrips" in his report to the same society for 1901. 2 In the 

 report for 1900 he states that these two species were found feeding 

 in unopened pear blossoms near Dublin, and he attributes the failure 

 of the fruit that season to the work of these insects. The report, for 

 1901 states that a Dr. Barton tried a dressing of kainit around the 

 trees, with very satisfactoiy results. 



In December, 1914, Mr. W. M. Scott 3 reported the occurrence of 

 the pear thrips in a Kieffer pear orchard near Baltimore, Md. The 

 insect was so abundant as completely to destroy the crop of fruit. 



THEORIES AS TO ORIGINAL HOME. 



Various ideas have been advanced as to the original home of the 

 pear thrips. Dr. Pietro Buff a, a well-known student of Thysanoptera, 

 in private correspondence under date of April 17, 1909, suggested that 

 while it is a good species it should be put only in the genus Physopus, 

 and expressed the belief that it was not a European species. Prof. 

 Silvestri suggested that it was introduced from China or was of other 

 oriental habitat. Several leading fruit growers have expressed the 

 belief that the insect was introduced into this country from France 

 or England, giving as the reason its apparent partiality to prunes, 

 which are varieties of European plums. 



The occurrence of the pear thrips in England lends some weight to 

 the theory that it is of European origin. It may be that natural 

 conditions hold it in check in England and that its advent into Cali- 

 fornia under conditions more suitable for its rapid increase explains 

 its presence there in such enormous numbers. Now, however, that 

 its presence is definitely established in the eastern United States, it 

 is probable that the insect had been in this country for years before 

 it was discovered. 



It may be possible that the pear thrips is native to the Santa Cruz 

 Mountains, with some wild rosaceous plant as its original food plant. 

 Upon this supposition it is probable that it has been present in the 

 Santa Clara Valley for many years, and that it first became notori- 

 ously destructive with the advent of favorable conditions. While 

 this species has been taken upon a great variety of plants and has 

 been found to be able to subsist on many of them, it is distinctly an 

 enemy of deciduous fruits, to which it shows a decided preference. 



COMMON NAMES. 



Many common names have been assigned to this insect, as "pear 

 thrips," "prune thrips," "cherry thrips," etc. The first mentioned, 



1 Carpenter, G. H. Report on economic entomology for the year 1900, p. 96-97. Reprinted from the 

 Report of the Council of the Royal Dublin Society for 1900. 



2 Carpenter, G. H. Injurious insects observed in Ireland during the year 1901, p. 153-154. In The Econ- 

 omic Proceedings of the Royal Dublin Society, v. 1, pt. 3, no. 5, July, 1902. 



3 Jour. Econ. Ent., v. 7, No. 6, p. 478-479, Dec, 1914. 



