822 Pomona College Jouknal of Entomology 



Let me also state in the beginning that well known fact that when the 

 eggs of female flies are developed after copulation, they must soon he laid l)e 

 there favorite host fruit present or not. Thus the spread of sueh a pest has 

 more to do with th^e food content of the fruits and adaptability to the growth 

 of the maggots than to the fact whether or not eggs are placed therein. I 

 have found cysts of undeveloped and dried-up eggs under the skin of leiiums, 

 very green guavas and papaias, showing that when sufficient favorable fruit 

 was not available, the eggs were laid upon the fruits nearest to the right 

 conditions. I also have noticed upon the star apple, a fruit containing a 

 quantity of quick hardening lacteal fluid in the skin, numerous female fruit 

 flies held solid by the hardening of this fluid on the ovipositor before ovi- 

 position was completed. Tests showed however that only a small percent of 

 eggs thus laid developed. 



I do not mean to say that the fly will deposit eggs in any and all fruits 

 promiscuously, but the many different kinds of fruits which breed the fly 

 show that it is able to adapt itself to many conditions. The limit of its 

 powers of adaptability to different kinds of host fruits is impossible to 

 determine, yet observation of its relation to certain styles of host fruits gives 

 basis for certain conclusions. 



The thickness or hardness of the skin of fruits is apparently not a 

 serious detriment to the development of this fly. In Australia \\ has been 

 bred from the passion fruit, which has a very hard skin, much resembling an 

 eggshell, though not brittle. Flies closely related, {Dacus cucurhitae), and 

 of very similar habits have been bred from the water lemon in Hawaii which 

 is very similar. The thickness of tiie skin then cannot be considered a 

 safeguard. 



The presence of certain acids in the fruits in small C|uantities does not 

 prevent development either if we can .iudge from the fact that the fly thrives 

 in oranges, grai)ofruit, and certain varieties of limes. As for lemons, we have 

 no record of its being bred from tliciii though we have evidence that the eggs 

 had been placed therein. 



As for juicy fruits, such as the peach, mango, etc., it is interesting to 

 note that the number of flies produced in proportion to the size of the fruit 

 is lower than in certain pulpy fruits. 1 have found that it is easy to drown 

 the maggots in the juice of decaying fruits in laboratory jars if too many fruits 

 were put in a single jar. The growth of the maggot rapidly causes a putrid 

 juice to form which, should the wliole fruit be full of maggots, would furnish 

 enough juice to drown probably the smallest ones, if not some more mature. 

 The instinct of the fly seems to regulate this so that not too many eggs are 

 laid in a fruit. ConseqiU'ntly, though the orange, for instance, is compara- 

 tively a large fruit, the number of flies bred per fruit is usually about 15 to 

 25. It is interesting to note that in addition to this fact with rcganl 1o the 

 peach, the fly stings tiiis fruit when it is still small and very green. 



Three pulpy fruits, however, give us some interesting data, namely, the 

 Coffee berry, the Mock orange {Mvrraya exotica), and the Kamani nut or 



