4 CIRCULAR 109, U. 8S. DEPARTMENT OF AGRICULTURE 
The records in Table 1 show for each species of host fruit the num- 
ber of fruits under observation, the number of maggots emerging, and 
the average infestation per fruit for each year of the 3-year period 
under consideration. The average infestation per fruit for the 9-year 
period, 1916-1924, inclusive, is given to show how these yearly 
records compare with the average for the nine years. By referring to 
Table 2 it will be noted that some fruits were collected only occas- 
ionally during the 9-year period. On the basis of comparisons only 
with those fruits upon which records were secured during five or 
more of the nine years, Table 1 shows that during 1922 the average 
infestation per fruit in 42.9 per cent of the species collected was greater 
than the average for the 9-year period. In 1923 this average was 
ereater in 26.7 per cent of the species of host fruits, and in 1924 it was 
ereater in 25 per cent of the host fruits. The percentage of host 
fruits having a higher infestation than the average has been well 
under 50 per cent during each of the three years of this period and has 
shown a decrease each year, indicating an actual decrease in infes- 
tation and in the number of adult flies. 
Table 2, showing the average infestation per fruit for each species 
of host during each year and for the 9-year period, 1916-1924, 
inclusive, is given to indicate the fluctuation of infestation from year 
to year. On the same basis as that outlined in the preceding para- 
graph, this table shows that the percentage of fruits having a higher 
average number of larvae per fruit in any yearly period than the 
average for the 9-year period is as follows: 1916, 56.2 per cent; 1917, 
50 per cent; 1918, 41.2 per cent; 1919, 46.7 per cent; 1920, 38.9 per 
eent; 1921, 71.4 per cent; 1922, 42.9 per cent; 1923, 26.7 per cent; 
1924, 25 per cent. These records show that during three years, 
1916, 1917, and 1921, the infestation was above the average in 50 
per cent or more of the fruits under observation. During the other 
six years less than 50 per cent of the host fruits showed infestation 
above the average, and in 1924 the percentage of 25 indicates that 
the infestation during that year was lower than for any other year 
covered by the table. 
PARASITISM RECORDS 
Owing to the oviposition habits of the parasites of the Mediter- 
ranean fruit fly now established in Hawaii, the effectiveness of these 
enemies in controlling the fly is governed to a large extent by the 
nature of the fruits in which the host maggots are developing. The 
three opiine parasites, Opius humilis, Diachasma tryoni, and Dia- 
chasma fullawayi deposit their eggs within the host larva by piercing 
the skin of the fruit and the integument of the larva with the ovi- 
positor. The host maggot must therefore be near the surface of the 
fruit in order to be within reach of the parasite. Consequently, in 
fleshy fruits which afford an opportunity for maggots to burrow some 
distance beneath the skin parasitism is low, whereas in small fruits 
and those containing a large seed covered by thin pulp, where the 
maggots are necessarily always near the outer surface of the fruit, 
parasitism is high. Tetrastichus giffardianus oviposits directly into 
the host maggot and must come directly in contact with the maggot 
before oviposition is possible. In order to reach host maggots 
within a fruit, it must be able to enter through some break in the skin. 
Fruits with tough skins which do not break readily when they fall 
