506 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 16 
Afternoon Session , September 18, 192J 
The excursion, previously announced, was attended by 30 members 
and visitors, who were shown the process of manufacturing nicodust and 
dusting machines, liquid hydrocyanic acid gas and calcium cyanide, and 
the methods of propagating and rearing parasites and predaceous insects 
for biological control. 
Morning Session , September 19, 192J 
The meeting was called to order by chairman R. E. Campbell who 
announced the order of business as a symposium on biological control 
under the leadership of H. S. Smith, in charge of Beneficial Insect 
Investigations, Univ. of Calif. 
The following papers were presented: 
WHAT MAY WE EXPECT FROM BIOLOGICAL CONTROL? 
By Harry S. Smith, University of California , Citrus Experiment Station 
Abstract 
Biological control work has been subject to extremes of popular approval and 
disapproval. This is due to a lack of understanding, on the part of the general 
public, of just what results may reasonably be expected from this method. Success 
is dependent upon biological principles with which the grower is not always familiar. 
Some insect pests are favorable subjects for attack by this method and others are not. 
It is pointed out that the proper co-relation between host and parasite and freedom 
from secondary parasites, are important factors in this type of control. The future 
is bright for this branch of economic entomology. 
The control of citrus pests by the use of their natural enemies is a 
phase of scientific agriculture which has appealed to California growers 
for many years. At no time since the introduction of the Australian 
ladybird, Vedalia, in the early 80’s, which resulted in the saving of the 
citrus industry from the ravages of the cottony cushion scale, has the 
California fruit grower lost interest in this method of pest control. 
His interest in the subject has not, however, been at a uniformly high 
pitch during this entire period. The introduction of Vedalia was nat¬ 
urally followed by a wave of enthusiasm for the introduction of parasites, 
not alone among growers but among some entomologists as well, which, 
as we have since learned, was hardly justified but which is easily under¬ 
stood in view of the striking results of this introduction. During this 
period the feeling was quite general in California that any pest could 
be controlled simply by the introduction of its parasite. 
For several years after the introduction of Vedalia enthusiasm was 
high; but failure to secure similar results with other insect pests had 
its effect and interest began to slacken somewhat. Then Scutellista, a 
parasite of the black scale, was introduced from South Africa in 1902. 
