FIELD WORK—RELEASE OF PARASITES. 25 
high hedge of Ambrosia trifida with scattered Solanum rostratum. 
As a further check on the experiment the nearest part of this field 
(‘“D,” fig. 5) was examined and proved to be parasitized by 2.1 per 
cent less than ‘‘A.”” On the contrary, the farther part of the field 
(‘‘B,” fig. 5) showed 5.8 per cent higher parasitism than “‘A.” The 
conclusion was that ‘““E”’ and ‘“‘D” did not influence “A.” 
The results are given in Table XIV for the entire experiment, and 
also according to species. It is believed by the writer that it was the 
release of Bracon mellitor which accomplished the change. 
The evidence upon which this belief is founded is both positive 
and negative. Bracon mellitor was not found breeding upon any 
other species of weevil in the vicinity, and yet the examinations 
showed an increase of parasitization by this species in the ‘‘ parasite 
oAD J 
eS 
ge COTTON 
8 
x 
S 
g 
nN 
& 
K 
8 
Ss 
cS 
e 
Fig. 5.—Diagram of cotton plantation of H. O. Samuel, Dallas, Tex., of 64.4 acres, showing location 
of plats where observations and experiments on boll-weevil parasitism were made. (Original.) 
ce 
area”’ opposed to a decrease in the ‘‘check area.’’ Catolaccus incer- 
tus, although released in large numbers, did not take hold at all,nor 
was it found breeding upon any other species of weevil in the vicinity. 
A few Cerambycobins C yaniceps were released, but the only trace of 
parasitization by this species was found in the original check. And 
yet this species was bred from Lirus musculus in the stems of Poly- 
gonum pennsylvanicum near by, and also from Trichobaris texana 
Lec., in the stems of Solanum rostratum adjacent to ‘‘A’’. No 
Eurytoma tylodermatis were released, although this species was abun- 
dant throughout the field. It is known as a parasite of Lixus scro- 
bicollis Boh., which breeds in Ambrosia trifida stems. Immense 
numbers of this plant were growing along the road adjacent to “A.” 
In order to show that plat ‘“E,’’ which was highly parasitized by 
