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 Jloridensis 
and concluded therefore that these were the camphor thrips in their 
native habitat. Careful and extended investigations by the junior 
author, however, have show this bav 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 
d characters ^ ^rd segment especially larger and more 
of antennee of the camphor slender in shape (fig. 2) ; stronger spines on the 
AntennT of camphor thrips:' head and thorax and a much smaller number 
Eml?ged na ° f bay thrips " of doubled hairs on the 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 
