Sept. 33, 1918 
Mediterranean Fruit Fly in Hawaii in 1917 
609 
varieties of mango and avocado not ordinarily susceptible to prohibitive 
infestation except under conditions permitting an unchecked multi¬ 
plication of the fly. This point has come to light during 1917, and the 
statement seems justified that a 50 per cent reduction in the numbers 
of the fly brings little relief to its favored host fruits, but that those fruits 
classed as unfavored hosts show a marked improvement in the degree of 
infestation, and some may become almost wholly free from larvae. The 
propagation of such fruits and the encouragement of the parasitic method 
of control would seem to be the most favorable method of contending 
with this pest in Hawaii. 
Table III .—Total parasitism , by month, of all larvce of Ceratitis capitata collected in 
Hawaii during 1917 
Percentage of parasitism. 
Month. 
Number 
of larvae. 
Opius hu¬ 
milis. 
Diachasma 
tryoni. 
Diachasma 
fullawayi. 
Tetrastichus 
giffar di¬ 
anus. 
Total 
in 1917. 
Total 
in 19x6. 
January . 
6,183 
39*0 
IS.6 
2.0 
2.4 
59 * 0 
6.98 
February. 
4 , S 68 
20 . O 
8.6 
3*0 
1*3 
3 2 * 9 
19-S 
March. 
5 ) 901 
27. I 
22. 5 
12 . 6 
1*3 
^ 3*5 
14.7 
April. 
2,861 
9*0 
27.6 
5*5 
I. 2 
43*3 
37 -64 
May. 
4,439 
8.8 
26.4 
3*4 
2*3 
40.9 
26. 69 
June. 
S, 9 r 9 
11. 7 
16. 3 
* 3 
7.8 
36.1 
27. 8l 
July. 
4 , 12 S 
3*9 
26. 6 
*9 
19.6 
S*-° 
18. 52 
August. 
8, 726 
2.8 
16. 4 
4*7 
9*2 
33 *i 
37*5 
September. 
9,047 
5*2 
3 i *3 
13*2 
2.7 
52.4 
45*2 
October. 
11,309 
7.2 
16.4 
13.2 
8.4 
45*2 
44-3 
November. 
5,919 
17.2 
22.6 
11.6 
20.9 
72.3 
44.3 
December. .... 
3 ,i 42 
5*3 
16. 7 
5*2 
7.0 
34-2 
44.1 
Average, 1917. 
72.139 
83.304 
12. 7 
20. 3 
7*3 
7.2 
47*5 
Average, 1916. 
17.2 
13*3 
2.1 
. 6 
33*2 
This 47 per cent reduction in the abundance of the fruit fly in Hawaii 
serves another purpose well worthy of mention. It is an important 
help contributing toward reducing the chances of its introduction to the 
mainland. 
As shown elsewhere by the writers, the parasitism by the braconid 
Opius humilis Silvestri has been found highest during the coolest months 
of the year. Again during 1917 this was observed. The parasitism by 
0 . humilis exceeded that of all of the other parasites combined in the 
months of January and February and was greater than that of any of the 
others taken separately during March. During the remaining months 
the parasite Diachasma tryoni was more abundant than the O. humilis . 
It is in the cool months of January, February, and March that the other 
parasites are so retarded that the O . humilis is enabled to gain a consid- 
4 erable foothold. 
