BULLETIN 1225, U. S. DEPARTMENT OF AGRICULTURE. 



ORIGIN. 



The original theory of Watson (5) regarding the origin of the cam- 

 phor thrips was that it had been introduced into Florida on nursery 

 stock from the Orient and was therefore peculiar to the camphor. 

 Since camphor trees are not indigenous to the United States, this 

 seemed to be a reasonable explanation. Later investigations, how- 

 ever, tended to show that the thrips might be a native insect and had 

 taken to the camphors because of their close relationship to its natural 

 hosts. Watson (11) states that the bay trees of the genus Persea 

 (Tamala) are the natural hosts of the camphor thrips. He found a 

 thrips on the bays which was very similar to Cryptothrips fioridensis 

 and concluded therefore that these were the camphor thrips in their 

 native habitat. Careful and extended investigations by the junior 

 author, however, have shown this bay thrips to be a new, although 

 closely related species. It was therefore described (12) as Crypto- 

 thrips laureli n. sp. Because of the close simi- 

 larity of the adults in the two species, as well 

 as the relationship of their hosts, it was reason- 

 able to believe from a superficial examination 

 that they might be the same species. There are, 

 however, some distinguishing structural char- 

 acters which were revealed after a study of the 

 immature forms and habits had shown them to 

 be distinct from the camphor thrips. 



COMPARISON OF BAY THRIPS AND CAMPHOR 

 THRIPS. 



The camphor thrips is fully described in later 

 pages. The bay thrips differs from it in the 

 following structural characters: Larger size; 

 antenna? longer and darker colored and with 

 the third segment especially larger and more 

 of antennae "oF «ie" camphor slender in shape (fig. 2) ; stronger spines on the 

 Anterma^f^amphor^t^rips: head and thorax and a much smaller number 



&nfid? a ° f bay thriPS of douDle(i hairs on tne fringe of the fore wings. 

 The eggs are larger also than the eggs of the 

 camphor thrips, are light straw-yellow instead of black, becoming 

 red during the development of the embryo, and are covered with 

 irregular scale-like patches rather than the regular hexagonal pat- 

 tern (fig. 5) of the camphor thrips. The distinguishing character 

 of the larva and the pupa is the bright and conspicuous carmine 

 red color compared with the dull orange red of the camphor thrips. 

 The time required for development is also longer in all stages. In 

 the adult stage different feeding habits are found, and usually sexual 

 reproduction instead of parthenogenesis. 



The food preferences of these two thrips are also different. 

 Although the bay thrips can be made to live on camphor, no instances 

 have ever been found in which it had taken to the camphors naturally. 

 Its natural hosts include only the four species of Persea which are 

 native of Florida (4). On the other hand, the camphor thrips will 

 live on camphor only and could not be made to live on bay, as will^ 

 be shown in detail later. Several generations of the bay thrips 



Fig. 2.— Structural characters 



