26 BULLETIN 616, U. S. DEPARTMENT OP AGRICULTURE. 



trees. Adult thrips suffer from the lacewings only when the weather 

 has become so cool as to make the thrips sluggish. 



In its early larval stage, the lady beetle (Hippodomia convergent 

 Guer.) feeds upon the citrus thrips. Although this Coccinellid is 

 extremely numerous throughout the Tulare County citrus belt, it 

 feeds mostly upon aphids and other larger insects which occur on 

 orange trees and more particularly on truck crops, and is of no 

 great importance in destroying the thrips. 



A thysanopteron enemy of the citrus thrips which seemed to be 

 increasingly important in 1912 was the 6-spotted thrips (Scolothrips 

 sexmaculatus Perg.). The principal food of the 6-spotted thrips, 

 however, appears to be mites which occur mainly on plants other than 

 citrus in Tulare County and which are not numerous enough on 

 orange to attract large numbers of the predatoiy thrips. This 

 thrips is apparently just learning the possibilities of abundant food 

 offered by the citrus thrips, and perhaps will feed more extensively 

 upon it as time goes on. It is apparently unable to catch the adults 

 and therefore feeds only upon the larvse. 



The younger nymphs of one of the assassin bugs (Zelus renardii 

 Kolen) 1 are fairly common upon orange trees in Tulare County and 

 have several times been seen feeding upon larvse of the citrus thrips. 

 The more advanced assassin bugs, however, feed principally upon 

 larger, and often harmless, insects and it is only in their first and 

 early second instars that they attack thrips. 



The small reddish nymph of the plant bug {TripKLeps insidiosus 

 Say) has occasionally been seen feeding upon flower thrips in orange 

 and several other blossoms. When imprisoned with Scirtothrips 

 citri it flourished very well upon the latter, but when the flower 

 thrips (Frankliidella tritid Fitch.) was also placed in the bottle the 

 latter proved more attractive to the insect, doubtless because of its 

 larger size and greater sluggishness of movement. Triphleps in- 

 sidiosus has not been seen upon orange trees after the blossom period, 

 when the flower thrips, upon which they mostly feed, have left the 

 trees. 



INTERNAL PARASITES. 



Thus far no internal parasites have been found attacking the 

 citrus thrips. Although the Chalcid parasite of Thysanoptera 

 (Thripoctenus russelli Crawf.) 2 has been found by the writer in the 

 San Joaquin Valley affecting the bean thrips (Heliothrips fasciatus 

 Perg.) and the flower thrips (Frankliniella tritid Fitch.), for some 



1 Identified by Otto Heideman. 



2 This parasite was first reared from Heliothrips fasciatus Perg. by H. M. Russell (see 

 TJ. S. Dept. Agr., Bur. Ent., Tech. Ser. Bui. 23, pt. 2, Apr. 27, 1912). It was described as 

 a new genus and species by J. C. Crawford in 1911 (see Proc. Ent. Soc. Wash., vol. 13, p. 

 233, 1911). 



