Summary.

The results of field and laboratory observations indicate that larvae of Culex (Lutzia) halifaxi (Dipt. Culicidae) and of Zygoptera (Odonata), and adults of Gyrinus sericeolimbatus (Col. Gyrinidae), Limnesia jamurensis (Acarina, Hygrobatidae), and perhaps of various species of Gerridae (Hemiptera) are among the most effective predators of larval anopheline mosquitoes at Palmalmal.

Of lesser importance in the control of Anopheles, although useful predators of culicine mosquitoes, are Hydaticus litigiosus. Copelatus sp. (Col. Dytiscidae), Enithares bergrothi (Hem. Notonectidae), and Orthetrum villosovittatum and other Anisoptera (Odonata).

Spiders of the genera Epeira and Meta, which spin webs over breeding pools, bats, and the house gecko Gehyra oceanica are of some importance as predators of adult mosquitoes.

Megarhinus inornatus (Dipt. Culicidae) is worthy of consideration as a biological ally in future campaigns against the scutellaris group of the genus Aëdes, as its breeding habits parallel those of the latter mosquitoes.

The introduction of Enithares bergrothi into metal tanks and drums in the Jacquinot Bay area should provide a practicable means of controlling the breeding of “domestic” mosquitoes when other methods are undesirable.

With the exception of M. inornatus, the predators discussed in this paper are probably of purely local importance.

There may be sufficient aquatic predators in certain permanent pools to control the breeding of anopheline mosquitoes effectively. Treatment with such larvicides as D.D.T. will destroy these predators as well as any mosquitoes present. Unless larvicidal treatment is repeated on a weekly basis, Culicidae will quickly establish themselves in the absence of their enemies; and pools that had been of little importance as mosquito breeding places will become major centres of anopheline development.