Apparent Changes in the Abundance and Distribution of Anopheles Species on Grenada Island1

Results of a recent survey of the 3 species of Anopheles mosquitoes, Anopheles (Nyssorhynchus) aquasalis, Anopheles (Nyssorhynchus) argyritarsis, and Anopheles (Anopheles) pseudopuncfipennis, on the island of Grenada are contrasted with the only other published survey of these species on Grenada, which was published in 1938. Results suggest that a significant change in the abundance and distribution of each species has occurred over this period. Physical characteristics of the aquatic habitats for each species are described and compared. INTRODUCTION sails and An. pseudopunctipennis, have been Grenada Island, located in the Eastern Caribbean, is the most southerly of the Windward islands, situated 12ON and 6 low. The island is 19 km wide, 34 km long, and lies 160 km north of the Venezuela coast. Grenada is a volcanic island and Mount St. Catherine is the highest peak at 840 m above sea level. The mountainous and thickly wooded island has a large number of streams and rivers. Intensive agriculture, the major activity on the island, has changed the environment in some areas from forests to numerous fields of cocoa, nutmeg, bananas, various spices, fruits, and vegetables. The tropical climate of Grenada is characterized by a distinct dry season from January through May and a wet season from June through December. Anopheles (Nyssorhynchus) aquasalis Curry, Anopheles (Nyssorhynchus) argyritarsis Robineau-Desvoidy, and Anopheles (Anophe1es)pseudopunctipennis Theobald are the 3 species reported from the few anopheline surveys conducted in Grenada. Anopheles argyrifarsis was the only Anopheles species reported by Macdonaid (1 9 16). Howard et al. (1 9 17) mentioned that Anopheles (Nyssorhynchus) farsimaculata Goeldi (=An. aquasalis), An. argyritarsis, and An. pseudopunctipennis were collected in Grenada. Root and Andrews (1 938) in a comprehensive wet season survey collected the same 3 species with the following comparative abundance: An. aquasaUs, 18.7%; An. argyritarsis, 30.0%; and An. pseudocumented as important vectors of human malaria parasites in many countries of Central and South America (Simmons 194 1). Throughout its range An. pseudopunctipennis is generally the dominant vector in mountainous areas during the dry season (Shannon et al. 1927, Aitken 1945, Rodriguez and Loyola 1989). In 199 1 we initiated a study on the population genetics of this species from the southern United States to northern Argentina, including the Caribbean region. Anopheles pseudopunctipennis was first described by Theobald (1 90 1) from Grenada Island (Lesser Antilles). The original description was not adequate for accurate identification of the species. This resulted in confusion and misidentifications of the species in other parts of its geographical range in North, Central and South America. Three names currently in synonymy, 5 subspecies and one variety have been applied to this species in South America (Knight and Stone 1977). Anopheles (Anopheles)franciscanus McCracken was also confused with this species for many years. Aitken (1945) stated: "No description of the egg, larval, and pupal stages, or of the male terminalia ofAn. pseudopunctipennis have been made from the type-locality" (Grenada). Objectives of our study in Grenada were to collect topotypic specimens of An. pseudopunctipennis, to redescribe and fully illustrate the species in all life stages, and to study its present abundance and distribution on this island. dopunctipennis, 5 1.3%. Two species, An. aqua-