20 



BULLETIN 122-5, U. S. DEPARTMENT OF AGRICULTURE. 



On July 7 a wire cage was placed over a small bay tree, P. horbonia, 

 planted near the laboratory, and several thrips in all stages released 

 in it. Many more thrips were added to the tree at intervals of every 

 few days until September 10. In no case were any live thrips found 

 on the tree more than one day after releasing them. 



All of these experiments prove that the camphor thrips will not 

 live on bay trees for any length of time. The adults in a few cases 

 have survived for a short time, but they will not reproduce and 

 maintain themselves there. 



AVOCADO. 



The avocado, being a close relative of the camphor tree, was also 

 tried as a food plant. Cuttings from the limbs were used as food in the 

 same manner as in the experiments with camphor and bay twigs. 

 The results as recorded in Table 5 are similar to those obtained with 

 the bay. Most of the larvae died before becoming adult. The adults 

 lived a maximum of 31 days. Although many eggs were laid in the 

 cages and a few of them hatched out, the young larvae would not live 

 on the avocado and soon died. 



Ta^le 5. — Length of life of camphor thrips on avocado (1920-21). 

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



Date. 



Number 

 placed on 

 avocado. 



Died. 



Dec.23 



3 a, 51 

 5a, 51 

 4a, 41 

 la. lp.. , 



Dec. 31, 21; Jan. 7, 1 1; Jan 10, 21; Jan. 17, 2 a; Jan. 20, 1 a. 



Jan. 6, 1 a; Jan. 8, 1 a; Jan. 10, 2 a, 1 1; Jan. 15,2 a; Jan. 17, 2 a; Jan. 23, 1 a. 



Dec. 30 



Jan.ll, 2 1; Jan. 12, 1 a; Jan. 18, 1 a; Jan. 21, 3 a; Jan. 22, 1 a. 

 July 8, 1 a; July 12, 1 a. 







A large number of camphor thrips were placed on a small avocado 

 tree in the laboratory yard, but after two days all had disappeared. 

 Other avocado trees are growing in a row of camphor trees which are 

 infested with thrips, but have never been found to have any thrips on 

 them. 



On March 7 some cages containing both adults and larvae from cam- 

 phor trees were tied over limbs of a large avocado tree. After one 

 month the cages were opened and one of them was found to contain 2 

 young larvae of the camphor thrips. These larvae certainly had been 

 reared from eggs laid by the adults in the cages. Three weeks later, 

 however, no thrips could be found in the cage, and it was concluded 

 that the camphor thrips can not maintain itself on the avocado tree. 



SASSAFRAS. 



In a similar manner efforts were made to feed camphor thrips on 

 sassafras, also a tree closely related to camphor. The results were 

 similar to those recorded for the bay and the avocado. Practically 

 all the larvae died before reaching maturity, and the greatest length of 

 life for the adults was 30 days. Most of them died after about two 

 weeks. A very few eggs were deposited, but in no case did any of the 

 larvae hatching therefrom live. 



