98 



BULLETIN 536, U. S. DEPARTMENT OE AGEICULTUEE. 



While it will probably take a number of years to determine just 

 what advantage the longer ovipositor will afford Diachasma tryoni 

 and D. fullatvayi over Opius humilis, the data in Table XXVII 

 clearly demonstrate the value of the cannibalistic habits of the newly 

 hatched larva to the more slowly developing species. 



Table XXVII.— Percentage of parasitism by Opius humilis and Diachasma tryoni in 

 larvx of Ceratitis capitata in Kona, Hawaii. 





Dates of 



larval 



emergence, 



1915. 



Percentage of para- 

 sitism. 



Locality. 



Dates of 



larval 



emergence, 



1915. 



Percentage of para- 

 sitism. 



Locality. 



Opius 

 humilis. 



Dia- 

 chasma 

 tryoni. 



Total. 



Opius 

 humilis. 



Dia- 

 chasma 

 tryoni. 



Total. 



Kainaliu 



Honaunau... 



Jan. 15-16 

 Jan. 16-18 



Feb. 6-8 

 Mar. 15-18 

 Mar. 18-19 



June 18-19 

 June 19-20 

 June 20-21 



(Jan. 19-20 

 {Feb. 9-10 

 I Mar. 19-24 



97.6 

 92.7 



85.3 

 92 



85.1 



63 



50.7 



56 



82.8 

 64.2 

 73.9 



0.8 

 .8 



9.3 

 

 



30.4 

 41.5 

 32.7 



3.4 



4.7 



.6 



98.4 

 93.5 



94.6 

 92.0 

 85.1 



93.4 

 92.2 



88.7 



86.2 



68.9 

 74.5 



Honaunau... 

 Kealakekua . 



Mar. 24-26 

 June 17-18 

 June 19-20 



Sept. 19-20 

 .Sept. 20-21 



Feb. 6-8 



June 16-18 



Sept. 18-19 

 Sept. 19-20 

 LSept. 20-21 



81.2 

 46.7 

 40 



13.9 

 10.6 



79 



31.4 



17.6 



23 



37.3 





 40.3 

 49.6 



65.1 

 69,6 







23.9 



67.6 

 56.4 

 48.3 



81.2 

 87.0 

 89.6 



79.0 

 80.2 



79 



55. 3 



85.2 

 79.4 

 85.6 



Data previously published by the writers have shown that 0. 

 humilis itself is capable of killing as high as 80 to 100 per cent of 

 the larvae of Ceratitis capitata developing in coffee cherries in the 

 Kona district of Hawaii. The data secured during 1915 showed 

 that there was a decided increase in the percentage of parasitism 

 caused by D. tryoni. This increase, however, as shown by the data 

 of Table XXVII, was largely at the expense of 0. Jiumilis, since the 

 total percentage of parasitism was not in excess of that which O. 

 humilis could have brought about by its own efforts. In the absence 

 of large amounts of data necessary to the definite establishment of 

 this point, the writers are of the opinion that similar fluctuations in 

 the relative importance of humilis and tryoni are likely to occur each 

 year unless fullawayi becomes thoroughly established, in which case 

 it is likely to supplant tryoni. The gradual increase in the abund- 

 ance of tryoni during the year is accounted for by the gradual removal, 

 as the summer months approach, of the restrictions upon parasite devel- 

 opment which cause a greater relative acceleration in the development 

 of tryoni than in the case of humilis. This, aided by cannibalism, 

 explains the ascendancy of tryoni during the summer and of humilw 

 during the colder winter months. It would appear that 0. capitata 

 in the coffee sections of Hawaii would have been quite as effectively 

 controlled had no opiine other than humilis been introduced. 



It is doubtful if the same fluctuation in the relative abundance of 

 tryoni and fullawaiji on the one hand and of humilis on the other 



