THE THYSANOPTERA OF CALTFORNTA." 41 



berries have no special value commercially, but in their perfect .state 

 are used extensivel}^ for Christmas decorations. 



The onion thrips {Thrlps tahacl Lind.) finds an almost ideal habitat 

 in the extensive onion-seed farms in California, and its injury to this 

 plant in' some sections and during some years is almost prohibitive of 

 onion growing'. 



Especially to be mentioned, however, is the injur}^ caused by the 

 pear thrips {Euthrips py7'i Daniel). This is strictly a fruit-tree pest, 

 attacking as it does nearly all varieties of deciduous fruits. No other 

 thrips is recorded as having done so much damage as has this one, and 

 the problem for its control is a difficult one to solve. The writer's 

 experience has been that, outside of purely cultural methods, we have 

 no effective artificial means for checking it. Its natural insect enemies 

 are few, and from the very nature of the pest's life habits it can not 

 be controlled effectively 1)y those beneficial forms which are already 

 present. A parasitic fungus has for the time being proved a quite 

 effective check, but the weather conditions, moist and warm for two 

 years past (during 1905 and 1906), have been almost ideal for the 

 growth of such fungi, and it is extremel}- doubtful if this check 

 would prove at all effective under other conditions. The pear thrips 

 is limited in its distribution to the deciduous-fruit areas around San 

 Fi'ancisco Ba^. 



It is interesting to note the relations of some of the California 

 thrips to their food plants. Orothrlps I'eUoggll is found only in blos- 

 soms of manzanita and madroiia — both trees peculiarly Californian — 

 whose cup-shaped blossoms afford an ideal home for this striking 

 thrips. ^Eolothrips huwanali is common only in the wild California 

 lilac. Tnchothrips ilex is peculiar to the Christmas berry, and has 

 thus far been collected from no other plant. jKuthripspyriis limited 

 in its feeding to cultivated fruits. Cvyptotlvrlps californicus is most 

 often found under the old shells of the brown apricot scale {Lecanium 

 armeniacuni) and the black scale {Saissetia olese). It has been taken 

 from these places mostly during the winter, and it may be that it is 

 under the old shells onh^ for protection, but the writer suspects that 

 it may be a scavenger. 



In preparing this paper the writer has introduced descriptions of 

 genera onl}" when it has been necessary to extend the characters to 

 include California species. For other generic descriptions the reader 

 is referred to Hinds's monograph of the North American forms.'^ 



The already recognized characters of ovipositor, wings, antenna, 

 and mouth appendages are the principal ones here used in the keys for 

 classifying the species. In describing new thrips the writer has made 



" Contribution to a Monograph of the Insects of the Order Thyi?anoi)tera Inhabit- 

 ing North America. By Warren Elmer Hinds. Proc. U. S. Nat. Mue., Vol. XXVI, 

 No. 1310, pp. 79-242, Pis. I-XI, December 20, 1902. 

 23668—07 2 



