442 



Journal of Agricultural Research voi. xviii. No. s 



place in the most preferred host fruits — that is, in fruits that consistently 

 show high degrees of infestation. The great increase in the infestation 

 of the mango may be accounted for by the fact that some varieties are 

 much more susceptible to fruit-fly attack than others. In 1916 and 191 7, 

 infestation records were obtained from 1,317 and 648 fruits respectively, 

 which were collected from a large number of mango trees of different 

 varieties. Many of these varieties showed little or no infestation, and as 

 a result there was a low average infestation for each of these two years. 

 The scarcity of mangoes in 191 8 made it impossible to obtain more than 

 85 fruits, which were of varieties preferred by the fruit fly. This accounts 

 for the high average infestation of 24.4 larvae per fruit. Those fruits, 

 showing by their comparatively low average infestation that they were 

 not especially preferred as hosts by the fruit fly, contained no more, 

 and in a number of cases contained fewer, larvae in 191 8 than were found 

 in 191 7. This lack of increase in infestation of the less-favored host 

 fruits confirms the conclusion drawn from the parasite records of 191 7 

 (4) — that, although 50 per cent of the fruit-fly larvae are destroyed by 

 these parasites and other agencies, little relief is afforded the preferred 

 host fruits, while much benefit is derived from the decreased infestation 

 of the less susceptible host fruits. 

 This is shown in Tables I to III. 



Table I. — Extent of infestation of host fruits by larvce of Ceratitis capitata in Hawaii 



during igi8 



Host fruit. 



Indian almond {Terminalia catappa). .. 



Mango (Mangifera indica) 



Coffee {Coffea arabica) 



Strawberry guava (PjzdzMW cattleianum) 

 Black myrobalan {Terminalia chebula) . . 



Peach (Amygdalus persica) 



Satin-leaf {Chrysophyllum olivaeforme) . . 



Rose-apple {Eugenia jambos) 



French cherry (Ewgrewia uniflora) 



West Indian medlar (Mimusops elengi). 



Kamani {Calophyllum inophyllum) 



Yellow oleander (Thevetia neriifolia) . . . 



Carambola {Averrhoa carambola) 



Chinese orange {Citrus sp.) 



Guava {Psidium guajava) 



Loquat {Eriobotrya japonica) 



Noronhia emarginaia 



Number of 



fruits 

 collected. 



25.558 



85 



49. 130 



24, 585 



5.664 



815 



1,380 



1,302 



13,558 



12, 216 



888 



169 



81 



7.450 

 3.481 



5,343 

 280 



Number of 

 C. capitata 



larvae 

 emerging. 



252, 067 

 2,076 



f 7. 517 

 31,692 



27,047 



18, 248 



4,376 



8,568 



13, 026 



30, 680 



2, 119 



I, 009 



74 



13, 349 



29, 542 



9, 606 



323 



Average number of 

 larvae per fruit. 



1918. 



9.9 



24. 4 

 .6 



1-3 



4.8 



22. 4 



3' 2 

 6.6 



1. o 



2-5 



2. 4 

 6.0 



•9 



1.8 



8-5 

 1.8 



2. o 



5-9 



15.2 



3-4 



2.4 



5-7 



.6 



1.8 



4-5 

 2.6 



1916. 



9-5 



I- 7 

 ■5 

 1.6 

 7.0 

 20. 5 

 2. o 

 5-5 



Although Table I shows that the infestation of host fruits in general was 

 as great in 1918 as it was in 1917, Table II indicates that parasitism of 

 the larvae developing in the majority of the abundant host fruits was 



