PARASITISM OF MEDITEREANEAN FEUIT FLY IN HAWAII 9 



Indian almond is a good example of a fruit containing a large seed 

 surrounded by thin pulp. The opiine parasites were much more 

 effective than T. giffardianns during all periods for which records 

 were kept for the 3-year period with the exception of January, 1922, 

 and the last five months in 1923. During those five months large 

 numbers of this fruit were collected within an area of about four city 

 blocks, and owing to some undetermined cause T. gifardianus was 

 able to parasitize an unusually large number of the developing 

 maggots. 



The coffee berry is another fruit having a very thin pulp and large 

 seed. It is very seldom that T. giffardianns is reared from maggots 

 in this fruit, but the parasitism, by the opiine parasites is very high. 

 The 11.1 per cent parasitism in October, 1924, shown in footnote 1 of 

 Table 3, was the work of the melon fly parasite Opiusjletcheri Silvestri. 

 This parasite is occasionally reared from maggots of the Mediter- 

 ranean fruit fly, but the high parasitism recorded during the month 

 mentioned is very unusual. It was probably due to the fact that all 

 of the coffee containing the maggots from which it was reared were 

 collected in the Kona coffee fields on the island of Hawaii. Around 

 these fields the Chinese cucumber Momordica sp. grows wild and is 

 very abundant. The fruits of this plant are attacked freely by the 

 melon fly, Bactrocera cucurbitae Coq., the maggots of which in turn 

 are highly parasitized, resulting in an abundance of O.fletcheri about 

 the coft'ee fields. 



The mango is an example of a fleshy fruit Avith a comparatively 

 tough skin which does not break easily when the fruit falls. The 

 percentage of parasitism in this fruit by either the opiine parasites 

 or the chalcid T. giffardianus is not high. 



The guava, which is very abundant about Honolulu, has a very 

 thin skin and a deep pulp. The majority of maggots are beyond 

 the reach of opiine parasites, and this results in a very low degree of 

 parasitism by them. The thin tender skin of this fruit breaks easily 

 when the fruit falls to the ground or is often punctured by birds or by 

 coming in contact with some part of the tree. Consequently, T. gif- 

 fardianus is afforded an unusual opportunity to enter this fruit, and 

 the parasitism by this species is in almost every instance higher than 

 that by any of the opiine parasites. In a number of instances it was 

 higher than the combined parasitism of all three species of opiines. 

 These are mentioned as examples of the influence exerted by the 

 structure of the infested fruits upon the effectiveness of the fruit-flj^ 

 parasites, and this influence can be observed hj reviewing the records 

 in the table of the parasitism in other fruits. 



Table 3 shows that all four species of parasites will attack their host 

 in most of the fruits under observation. Though the structure of the 

 infested fruit controls to a large extent the parasitism by D.fullawayi, 

 the degree of its effectiveness in some fruits can not be attributed to 

 this cause. This parasite in the majority of host fruits is compara- 

 tively ineft'ective, whereas in coffee and yellow oleander its effective- 

 ness is greater than that of either of the other two opiine parasites. 

 This ma}' be an indication of some preference on the part of this 

 parasite for maggots in certain fruits. 



Table 4 records the effectiveness of each species of parasite in all 

 fruits collected during each month of the three years. 0. humilis was 

 first in effectiveness during three months in 1922, during no month in 



