THE MELON FLY IN HAWAII. 53 



unless great care is taken thoroughly to tamp soil filled in over such 

 infested material adults can emerge from pupae and finally burrow 

 their way to the surface from a depth of from 2 to 3 feet of dry sand ; 

 34, 8, and 5 adults, respectively, from lots of 500 pupae buried 2 feet 

 deep succeeded in reaching the surface through dry sand, wet sand, 

 and soil. Fifty-four 3-day-old pupae were placed in the center of 10 

 square inches of heavy black soil, such as is found in the market- 

 garden section of Waikiki. On drying out this soil hardened so that 

 no adults were able to emerge. One hundred larvae which had 

 emerged ready for pupation were placed on the surface of the same 

 heavy black soil just mentioned, which had been thoroughly wet, as 

 though well irrigated. All the larvae pupated on or close to the sur- 

 face and 70 yielded adults. The soil was so tenacious on drying that 

 the remaining 30 per cent which were just beneath the surface were 

 unable to emerge. 



Burial of the host for the destruction of the immature stages of 

 the melon fly is not a method of control to be recommended. The 

 labor necessary properly to bury infested material is so great that 

 few lots will be buried to a sufficient depth, and cracks formed in 

 the soil by rapid decay and settling furnish avenues for the escape 

 of adults from fully 95 per cent of all material, even when buried in 

 the most tenacious soils. 



Traps. — Howlett states 1 that he was able in India to attract the 

 males of the two closely related fruit flies, Dacus zonatus Saund. and 

 D. diver sus Coq., by exposing citronella oil. He was not able to attract 

 specimens of either sex of the melon fly. Although he was success- 

 ful in attracting these two species with citronella oil, he failed to 

 get any reaction with such individual derivatives of this oil as 

 were obtainable (citrol, citronella, geraniol, citronellaldehyde, cit- 

 ronellol). Later he believed that he had found the actual substances 

 which are responsible for attracting these two fruit flies in iso-eugenol 

 and methyl-eugenol. By exposing the closely related eugenol he 

 succeeded in attracting the male of an apparently new species. 

 Samples of eugenol sent by Howlett to Severin and given the writers 

 by the latter gentleman failed to attract melon flies when exposed in 

 infested districts. 



The mango fruit fly (Dacus ferrugineus Coq.) was found by Frog- 

 gatt (26) to be attracted by citronella oil, but Illingworth states 2 

 that the railroad worm (Rhagoletis pomonella Walsh) avoids cit- 

 ronella oil. It is now well known that the males only of the Medi- 

 terranean fruit fly are attracted in any numbers to ordinary kero- 

 sene. In Honolulu the writers have seldom caught adults of the 



1 Howlett, F. M. The effect of oil of citronella on two species of Dacus. Trans. Ent. 

 Soc. Lond., 1912, Pt. II, p. 412-418, pi. 39, 40. 1912. 



2 Illingworth, James F. A study of the biology of the apple maggot, etc. Cornell 

 Univ. Agr. Exp. Sta. Bui. 324, p. 160. 1912. 



