![Thumbnail: [Volume 76, 1946-47 page 472]](/journals/rsnz/images/rsnz_76/thumbnails/rsnz_76_03_0592_0472_ac_02.gif)
Class Amphibia.
Order Salienta.
Family Ranidae.
Rana sp.
Ground pools at Palmalmal, those of a temporary nature in particular, were often found to be swarming with tadpoles belonging to the genus Rana. Fully grown tadpoles kept in the laboratory devoured neither pupae nor late instar larvae of mosquitoes. Imagines emerged from all the pupae concerned; although several of these adults were knocked over and drowned during hatching by the vigorously moving tadpoles.
The results of experiments in which tadpoles of Rana sp. 2 5 cm. in length were supplied with early instar larvae and eggs of Culicidae as food are detailed in the following table.
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| Experiment number. | 1 | 2 | 3 | 4 | |
|---|---|---|---|---|---|
| Mosquito species supplied to the predator as food. | Anopheles farauti. | Culex pullus. | Anopheles farauti. | Culex pullus. | Mixture of both species. |
| Developmental stage supplied. | 1st instar larvae. | 1st instar laivae. | 1st instar larvae. | 1st instar larvae. | Eggs. |
| Average number of larvae or pupae eaten by a single predator each day. | 1.5 | 0.9 | 0.7 | 0.4 | 2.8 |
The few larvae and eggs destroyed in this investigation seemed to be encountered accidentally, rather than songht out, by the surface-feeding tadpoles.
![Thumbnail: [Volume 76, 1946-47 page 473]](/journals/rsnz/images/rsnz_76/thumbnails/rsnz_76_03_0593_0473_ac_02.gif)
Temporary pools containing great numbers of tadpoles were often heavily populated with the developmental stages of Anopheles punctulatus as well. Ross (1900) records that numbers of frogs and tadpoles inhabiting anopheline breeding places at Freetown, Sierra Leone, were apparently living at peace with the mosquito larvae.
It is evident from these field and laboratory observations that tadpoles are of little if any significance as predators of the Culicidae; although when large numbers of tadpoles and mosquito larvae inhabit the same pool it is probable that a proportion of the emerging mosquitoes are knocked over and drowned as a consequence of the constant agitation of the water surface by the tadpoles.
Such indirect control forms a natural parallel of various types of artificial control which aim at causing agitation of the water surface. An example of this type of artificial control is mentioned by Covell (1943), who states that in parts of Malaya pools on hillsides are fed by water from split bamboo conduits, the ends of which are supported about four feet above each pool. The resultant constant splashing and rippling of the water surface inhibits mosquito breeding.