44 MISCELLANEOUS RESULTS OF WORK OF BUREAU — IX. 



Under the name Thrips adonidum, A. J. Cook/ 1 writing of this spe- 

 cies, in 1874, said: "Around Detroit, here at Adrian, and in our south- 

 ern counties they are likewise a serious pest." 



In 1882 Mr. Th. Pergande 13 recorded this insect as taken out of 

 doors at Washington, D. C, on apple late in November. J. A. Lint- 

 ner, 15 in 1885, on this authority, lists it as an insect affecting the apple. 



Nothing more was written about this species in this country until 

 1896, when G. C. Davis 21 wrote of " a black species, Heliothrips lixmor- 

 rhoidalis, which we have found most common on croton plants. As 

 far as noticed its work is confined to the underside of the leaves, 

 where the spots are eaten, so that the work clearly resembles that of 

 the red spider." 



Dr. F. H. Chittenden, 24 in 1902, predicted that this species, which 

 he called the " greenhouse thrips," would probably increase in num- 

 bers and destructiveness with time. 



Hinds 25 wrote of this insect the same year: "It has been very inju- 

 rious in some places." He also added that it was called the "black 

 fly" in Germany and that its life history was unknown. 



RECENT RECORDS. 



This species, determined by Mr. Pergande, was sent in to the 

 Bureau of Entomology, January 8, 1908, by Mr. P. J. Wester, of 

 Miami, Fla. , who collected it on mango ( Mangifera indica) . He wrote : 

 "It has never appeared to do serious damage until this year." 

 Mr. I. J. Condit, a collaborator of this bureau, at San Luis Obispo, 

 Cal., reported it injurious in a greenhouse at that place in September, 

 1908, and again reported it on November 2, 1908, as injurious to orna- 

 mentals in one of the parks at Santa Barbara, Cal. 



NATURE AND EXTENT OF INJURY. 



The damage caused by the greenhouse thrips is confined to the 

 foliage of ornamental plants entirely, in so far as the author is aware, 

 for he knows of no recorded injury to the blossoms of plants nor has 

 he noticed any. Injury effected by the thrips is due to the method of 

 feeding on the plants. Adults and larvae both obtain their food by 

 puncturing the epidermis of the leaf with their sharp mouth-parts, ° 

 and after lacerating the tissue they suck out tissue and plant juices 

 at the point of attack. The insects then attack the leaf in a new 

 place, so that in time it becomes full of tiny, pale-colored spots where 

 the tissue and chlorophyll have been extracted. 



In the case of croton plants, upon which this insect was studied, 

 injury was noticed first on the older leaves and gradually, as these 

 became badly infested, the injury spread until the young leaves were 



a For structure of mouth-parts see "The Pear Thrips," by Dudley Moulton, Bui. 

 Part I, Bur. Ent., U. S. Dept. Agr., pp. 2-3, 1907. 





