The Physico-chemical Factors of Water in Relation to Mosquito Breeding in Trinidad

Abstract

1. An analysis of rice-field and canal waters was made over a period of 1 year.2. The incidence of Anopheles tarsimaculatus in these fields and canals was noted.3. The chemical factors estimated were pH, carbon dioxide, organic nitrogen, dissolved oxygen, nitrites, nitrates, phosphates and ammonia nitrogen.4. No correlation was found between the incidence of A. tarsimaculatus and the following factors: pH, carbon dioxide, organic nitrogen, dissolved oxygen, nitrites, nitrates and phosphates.5. In nature the female A. tarsimaculatus seemed to prefer waters with a low ammonia nitrogen content, larvae being rarely found in water with a content greater than 0·04 parts per 100,000. In the laboratory the larvae of A. tarsimaculatus lived several days in waters with an ammonia nitrogen content as high as 0·12 parts per 100,000. Therefore it was concluded that ammonia nitrogen had some bearing upon the prevalence of this Anopheles, affecting the oviposition of the female rather than the growth of the larvae.