THE CAlkPHOR THRIPS. 



19 



that the camphor thrips might have been a native insect living on 

 some of these trees, and had taken to the camphor because of their 

 close botanical relationship. No evidence to support this theory has 

 been found, however. 



BAYS. 



Efforts were made to rear the camphor thrips on twigs of bay 

 trees cut and brought into the laboratory, using the same type of 

 cage as previously described for the life-history work on camphor 

 twigs (fig. 6) . The results of this work are given in Table 4, which 

 shows the length of time each lived. Three species of bays were used, 

 the swamp bay, Persea palustris, the red bay, P. borbonia, and the 

 shore bay, P. littoralis. Observations were made on the scrub bay, 

 P. Jiumilis, in its natural habitat, but trees of this species were not 

 available near the laboratory where they could be used for experi- 

 mental feeding. 



Table 4. — Length of life of camphor thrips tvhenfedon bay-tree twigs (1920-21). 

 [a=adult; l=larva; p=pupa.] 



Date. 



Number 

 placed 

 on bay. 



Died. 



Dec. 14 



5a,51 

 5a,51 

 4a,41 

 4 a, 41 

 4 a, 41 



3a 



4a 



2a 



81 



Dec. 27, la, 41; Dec. 30, lp; Jan. 3, la; Jan. 6, la; Jan. 8, la; Jan. 10, la. 



Dec. 14 



Dec. 20, 2 1; Dec. 22, 3 1; Dec. 24, 2 a; Dec. 27, 1 a; Dec. 29, 1 a; Dec. 30, 1 a; 



Dec. 30 



Jan. 4, 41; Jan. 11, 3 a; Jan. 18, 1 a. 



Jan. 18 



Jan. 22, 4 1, 1 a; Feb. 2, 1 a; Feb. 8, 1 a; Feb. 10, 1 a. 



Jan. 18 



Feb. 8, 3 a, 4 1; Feb. 10, 1 a. 





June 13, 1 a; June 16, 2 a. 



June 22 , 



July 5 



June 27, 4 a. 



July 9, 1 a; July 11, 1 a. 



July 9 3 1; July 11, 1 a, 3 1; July 12, 1 1. 



Aug. 11, 4 1; Aug. 15, 1 a. 



Aug. 7, 1 a; Aug. 11, 3 a. 



July 5. 





51 





4a 



91... . 



Aug. 23 



Aug. 24, 41; Aug. 26, 51. 







The data in Table 4 show that camphor thrips larvae can not live on 

 bay-tree cuttings. In a few cases they became adult, but most of the 

 larvae died after a few days. The adults lived longer, one of them 

 reaching 23 days. In nearly all of the cages the adults laid some eggs, 

 but more of them were on the cotton stoppers than on the bay-tree 

 twigs. In only a very few cases did any eggs hatch, and the young 

 larvae could not then be found. They evidently died from lack of 

 proper food. 



Thrips were also placed in cages tied over limbs of a growing bay 

 tree. On March 15, 1921, 5 cages containing 20 thrips each, in all 

 stages, were tied on limbs of Persea palustris. On opening the cages, 

 April 6, some adults were found in one cage only. No eggs or larvae 

 were present. June 4 the cages contained no thrips in any stages. 

 They evidently failed to reproduce on the bay tree. 



A similar experiment was performed later on the same tree. Three 

 small wire cages were tied on limbs of the tree on August 12, and a 

 dozen thrips liberated in each. After 6 days they were opened and no 

 live thrips or eggs could be found in any cage. 



On May 6 several cages containing a dozen thrips each were tied on 

 limbs of the shore bay, P. littoralis, at Daytona Beach. After 7 days 

 one cage was found to have a few live adults, but on May 28 no thrips 

 or eggs could be found in any cage. 



