2 CIRCULAR 109, U. S. DEPARTMENT OF AGRICULTURE 
duced from Australia. Other parasites were introduced, but the 
four mentioned were the only ones that became established. The 
uniform climate of Hawaii and the constant abundance of host 
maggots resulted in a rapid dispersal of these parasites, and within 
three years after liberation they were firmly established on the main 
islands of the Territory and were parasitizing between 30 and 50 per 
cent of the fruit-fly larvae. 
Since these parasites became established the Bureau of Entomology 
of the United States Department of Agriculture has compiled a com- 
prehensive series of records which show the amount of parasitism 
accomplished by each species and the degree of infestation of host 
fruits by the fly. These records have been obtained by making almost 
daily collections of host fruits about the city of Honolulu and securing 
from them the maggots as they emerged. These maggots were held 
in rearing jars and the numbers of emerging flies and parasites care- 
fully recorded. In this manner the effectiveness of each species of 
parasite has been determined over monthly and yearly periods since 
1914 for the various host fruits. The results of these observations 
up to ca including 1921 have already been published (1, 2, 4, 6, 
a9, 10): 
During the first few years after the parasites were liberated in 
Hawaii yearly reports of their activities were of much interest. In 
that period there was considerable yearly variation in the effectiveness 
of each species and in the total parasitism by all species. Conse- 
quently, during the years from 1915 to 1921, inclusive, these records 
for each year were published separately, excepting those for 1919 and 
1920 which were published together in one paper (9). The records 
for the last five years of this period, however, show that the work of 
the parasites has become more or less stabilized and that there is 
much less variation over yearly periods. Consequently, much of the 
necessity for yearly reports has disappeared, and a 3-year reporting 
period has been adopted and put into effect in this circular. It is 
believed that the reader can get a more thorough and comprehensive 
idea of the relationship and actual work of these parasites if the 
information for the period is included in one report instead of three. 
RECORDS OF INFESTATION 
In connection with the recording of parasitism, an attempt has 
been made to note any increase or decrease in abundance of Ceratitis 
capitata in the field. In making this attempt the following hypothesis 
was adopted: An increase or decrease in the number of maggots in 
infested fruits will indicate that there has been an increase or decrease 
in the number of adult flies. As all fruits collected for records of 
parasitism were held in the insectary long enough to allow all maggots 
to emerge, and as records of the numbers of all fruits and of the 
maggots emerging from them were kept, the average infestation per 
fruit for each species of host can be computed from these records. 
Tables 1 and 2 give the results of these observations and computations. 
