18 BULLETIN 1225, IT. S. DEPARTMENT OF AGRICULTURE. 



SEASONAL HISTORY. 



In the warmer parts of Florida the camphor thrips is active and 

 reproduces at all times of the year, but in the more northern parts 

 of the State, especially at Satsuma and Waller, where the largest 

 number of camphor trees are growing, it is doubtful if they reproduce 

 through the winter. Professor Watson states that breeding ceases 

 at Gainesville during the winter. Adults are known to hibernate 

 there, and it is difficult to find young larvae during the colder months. 

 Such is not the case at Orlando, however. The breeding experiments 

 recorded in this bulletin were conducted through the winter at the 

 laboratory in Orlando but under natural climatic conditions. Checks 

 and daily observations made on trees growing in the laboratory yard 

 have confirmed the results as given, and show that the thrips exist 

 in all stages throughout the year. 



During the late fall and winter months the thrips were especially 

 abundant on the trees at Orlando, perhaps more so than at any 

 other time of the year. On April 1 fewer thrips were noted, and 

 they continued to decrease in numbers for about two months. The 

 same condition existed at the camphor plantation at Satsuma. 

 During April and May very few thrips were in evidence, and the 

 camphor growers reported that they were never injurious at that 

 time of year. During June they began to appear in considerable 

 numbers and caused injury to the trees, being found mostly on the 

 young buds, many of which were blackened and killed. The thrips 

 continued to work on the trees throughout the summer, feeding on 

 the bark when there are no buds or new growth. At Satsuma their ac- 

 tivity ceases about November and little breeding takes place until 

 March, unless spells of warm weather occur during the winter. At 

 Orlando, however, they continued to live and increase on the camphor 

 trees throughout the winter 



It was always observed that no thrips were in evidence on the 

 trees on a cold morning. When the temperature was down to 

 50° F. they remained down in the bark lesions on the older limbs. 

 It was not until the sun had warmed up the atmosphere that they 

 would come out on the bark and leaves to feed. By cutting open 

 the lesions the insects could be found in all stages. They feed there 

 on the bark and cambium tissues and often remain for several days 

 at a time if weather conditions are unfavorable. In fact it is in 

 these lesions that the adults hibernate through the entire winter in 

 the northern part of the State. Cloudy or rainy weather even in 

 summer has a tendency to drive the thrips to the shelter of the 

 bark lesions. They show a decided positive reaction to sunlight and 

 are found in the tops of the trees on bright days only. 



HOST PLANTS. 



As far as is known, the camphor thrips will live only on the camphor 

 tree, Cinnamomum camphora (L.) Nees & Eberm. Experiments 

 were conducted to determine if it would live on other closely related 

 trees, including bays (Persea spp.), avocado, Persea americana Mill., 

 and sassafras, Sassafras variifolium (Salisb.) Kuntze. These are 

 included with the camphors in the family Lauraceae and are native 

 in the parts of Florida where the camphors grow. It was thought 



