UNEXPLAINED MORTALITY. 13 
in 1906, white flies were more abundant in 1907 in this grove than 
in any other grove or section in or near Orlando. 
The white-fly laboratory was located in grove No. 3 during 1906 
and 1907. This grove, the property of Hon. J. M. Cheney, is 
located immediately south of No. 2. The red Aschersonia was more 
abundant on a certain group of trees in this grove than on any other 
trees in the locality covered by these observations. The white flies 
were most abundant in this section of the grove in 1907, while in 
other sections, where only traces of the fungus occurred, the insects 
had become very scarce before September 1, 1906, and were least 
numerous in 1907. 
Grove No. 4 is the " Wilcox Grove," located immediately south of 
Mr. Cheney's grove (No. 3). The foliage in this grove was only 
slightly blackened at the time it first came under the observation of 
the senior author in August, 1906, the insects even then being on 
the decline in point of numbers. In this grove the fly was so effect- 
ively reduced that it did not multiply to the point of slightly blacken- 
ing the foliage until the fall of 1908. 
Grove No. 5 was known as the " William Dennen Estate Grove" 
and is located about one-half mile south of the city limits, imme- 
diately south of the Atlantic Coast Line Kailroad. This grove was 
so seriously injured in 1905 and looked so unpromising in the winter 
of 1905-6 that it was considered inadvisable by those in charge to 
go to the expense of fertilizing until some satisfactory method of 
control was discovered. In the spring of 1906, during an unfavorable 
period, the grove was sprayed twice, the adults being then on the 
wing. In this instance spraying was at first believed to be responsible 
for the cleaning up of the grove, but examination in several groves 
of the effectiveness of the applications made by the same spraying 
outfit, and the experience of the authors in their experimental work, 
eliminate beyond doubt the possibility that the two applications of 
sprays were responsible for the scarcity of white flies. Mr. E. H. 
Walker, chairman of the Orange County horticultural commission, 
who had general charge of the extensive spraying carried on in the 
Orlando district in 1906, agrees with the authors in considering that 
the spraying, whatever its effectiveness may have been by itself, 
could not have produced such striking results. The first trace of 
red fungus was found in this grove in the fall of 1908 by the senior 
author. By this time the white fly had increased to the extent of 
slightly blackening the foliage of a few trees. The greater effective- 
ness of the unexplained mortality in this grove (No. 5) as compared 
with the effectiveness of this factor throughout the city of Orlando 
was due to the absence of china-trees (Melia azedarach) and umbrella 
china-trees (Melia azedarach umbraculifera) in the immediate neigh- 
borhood. These trees, as explained in previous publications, 1 are 
i Bui. 76, Bur. Ent., U. S. Dept. Agr., 1908 (see Chinaberry); Bui. 92, Bur. Ent., U. S. Dept. Agr., 1911 
(see China-tree). 
