MEDITERRANEAN FRUIT FLY IN HAWAII. 77 



NATURAL CONTROL. 



No striking examples of control by natural agencies were evident 

 in Hawaii previous to the introduction of parasites. As indicated 

 below, there are several minor factors of natural control, aside 

 from parasites, but they are of no practical value under Hawaiian 

 conditions. A certain amount of natural mortality occurs among 

 larvae and pupae, but it is small under ordinary conditions. It has 

 been suggested that there occurs an unusually high mortality among 

 pupae formed by larvae developing in such juicy fruits as the mango, 

 but this has been disproved by experimental work. The high rate 

 of mortality among pupae derived from mangoes in laboratories is 

 produced by the severe sifting process necessary to separate the 

 pupae from the wet sand in which they form, or from insanitary 

 conditions. 



EXCESSIVE HEAT. 



The larvae within fruits which lie in the direct sunlight after they 

 have fallen are killed in large numbers. Often all the larvae in the 

 portion of a fruit exposed to the sun will be found dead. During 

 August, 1914, mangoes were exposed to the sun for two days over sand 

 in shallow trays. Examinations later proved the 17 fruits to contain 

 17 living and 84 dead third-instar larvae, with 14 larvae dead on the 

 surface of the fruits. One larva died when partly out of a fruit and 

 103 succeeded in pupating normally. In 23 other fruits held in the 

 shade as a check there were found 168 living and 9 dead third-instar 

 larvae, and beneath them 167 pupae. While every larva in certain 

 of the fruits exposed to the sun was killed, it is evident the many 

 larvae in the protected portion of the fruit may escape and pupate 

 normally. 



PREDACIOUS ENEMIES. 



Although Compere reported certain staphylinid beetles in Brazil and 

 f orficulids in India attacking larvae of fruit flies, they seem to be of little 

 value as practical checks. The writers have observed earwigs within 

 decayed areas of fruits infested by C. capitata and drosophilid larvae 

 in Hawaii under conditions which indicated that they were feeding 

 upon fruit-fly larvae. Earwigs confined in jars within the laboratory 

 were observed to attack and devour well-grown C. capitata larvae. 

 Their numbers, however, are far too small to have any effect upon 

 fruit-fly increase.. 



The small brown ant (PJieidole megacephala Fab.), known also as 

 the Madeira house ant and the harvester ant, unquestionably is an 

 important factor in natural control. This ant, which inhabits most 

 abundantly the littoral regions, is frequently found swarming over 

 and throughout fallen fruits, killing many larvae as they leave the 

 fruit to pupate. Ants were observed to remove from a fallen ball 

 kamani nut 86 medium sized C. capitata larvae between 11.18 and 

 11.58 a. m., April 5, 1913. An examination at the end of this period 



