40 MISCELLANEOUS PAPERS. 



the conditions in the Santa Clara Valley l)ecame so grave that some- 

 thing had to be done was an}^ very serious study given to these insects. 



Orange growers in southern California were made very apprehensive 

 a few years ago by the appearance of small brown spots on their 

 oranges, caused by the feeding of the grass thrips {EutJuHps trltic! 

 Fitch). The injury was, however, superticial, as a spot onl}^ was pro- 

 duced on the orange peel, the quality of the fruit being in no way 

 injured nor its qualities of keeping affected. Yet because of the spots 

 man}^ of the best oranges had to be passed out as culls. This same 

 thrips has been reported injuring alfalfa by its feeding within the 

 blossoms. The damage was hardly noticed when the alfalfa was cut 

 for hay, but for seed purposes the crop was an almost absolute failure. 

 The grass thrips is everywhere present in wild and cultivated Howers 

 and in blossoms of most of the indigenous trees. The writer has often 

 been able to collect hundreds of specimens of this thrips with a single 

 sweep of the net from the blossoms of the California sage {Artemisia 

 calif fyniica) ^ and from the manzanitas, especially Arctodaphylostomen- 

 tosa. This thrips is perhaps seen most commonly in our garden 

 flowers — roses, lilacs, etc. — and does little or no apparent injury. 

 Often, however, one tinds ill-shaped and partly dead outer petals of 

 rose buds or even full-l)lown roses. This injury, when not caused hy 

 mildew, can be quite easily traced to the grass thrips, which feeds in 

 the tip of the bud on the outer end of the petals, just before or while 

 the petals are spreading. This injury is common, but as roses unfold 

 rapidly, the larger, inner petals are not injured, and the outer, smaller, 

 imperfect ones may l)e picked ofi' and the rose left apparently perfect. 

 This species is perhaps the most widespread of all the thrips. Only 

 at intervals does its injury render it a pest. Its appearance is very 

 like that of the pear thrips {E'athrip.s pyri)^ and to the casual observer 

 either species could easily be mistaken for the other. 



The feeding injuries of IleUotkrip^ JuemorrJioldalis are limited 

 largely to azaleas, cherry laurel, and laurestina, and to greenhouse and 

 other ornamental shrubs. The writer has found in greenhouses azalea 

 plants which have been completel}^ killed by these insects. Affected 

 laurestina plants produce contorted, ragged, and pale leaves. 



The injury of Trh-liofhr'ipH ilex on the Christmas l)ei"ry {Ilctet'omelex 

 arbiitlfolia is noticeable wherever that plant grows. This insect has 

 been found onl}' on the one plant, and it is interesting to note that the 

 plant is indigenous only to limited areas in the Coast Range region 

 near San Francisco Ba}'. The Christmas berry is one of the 

 showiest of California shrubs when, from November to January, it 

 displays its line clusters of crimson berries. When the plants are 

 badly infested with thrips the leaves are deformed and ragged and 

 the weakened blossoms produce small and imperfect berries. The 



