Identification keys to the Anopheles mosquitoes of South America (Diptera: Culicidae). IV. Adult females

Abstract

Background: Morphological identification of adult females of described species of the genus Anopheles Meigen, 1818 in South America is problematic, but necessary due to their differing roles in the transmission of human malaria. The increase in the number of species complexes uncovered by molecular taxonomy challenges accurate identification using morphology. In addition, the majority of newly discovered species have not been formally described and in some cases the identities of the nominotypical species of species complexes have not been resolved. Here, we provide an up-to-date key to identify Neotropical Anopheles species using female external morphology and employing traditionally used and new characters.

Methods: Morphological characters of the females of South American species of the genus Anopheles were examined and employed to construct a species/group identification key. Photographs of key characters were obtained using a digital Canon Eos T3i, attached to a microscope. The program Helicon Focus was used to build single in-focus images by stacking multiple images of the same structure.

Results: A morphological identification key to the adult females of species of the genus Anopheles described in South America is presented. Definitions and illustrations of the key characters are provided to facilitate use of key.

Conclusions: Identification of species of the genus Anopheles based on female morphology is challenging because some key characters can be variable and overlapping among species. In addition, the majority of key characters are linked to color and shape of scales, their distribution on the head, scutum, abdomen, maxillary palpi, labium and legs, and pattern of pale and dark scales on dorsal and ventral surfaces of the wing veins. Thus, it is understandable that a specimen needs to be in good condition to be accurately identified. Morphologically similar species, such as those of the Konderi, Oswaldoi, Nuneztovari, Benarrochi and Albitarsis Complexes, and the Triannulatus and Strodei Groups, among others, cannot be accurately identified using characters included in the key. Further investigation will be required to exploit morphological characteristics for identification of members of those complexes, with formal description of new species.

Keywords: Anopheles; Identification; Illustrated key; Morphology; South America.

Fig. 1

Uni-lobed scutellum of an adult of An. (Ano.) pseudopunctipennis Theobald, 1901

Fig. 2

Tri-lobed scutellum of an adult of the genus Chagasia Cruz, 1906

Fig. 3

Head of a female of An. (Ano.) calderoni Wilkerson, 1991

Fig. 4

Thoraces of Anopheles spp., dorsal aspects. a An. (Ker.) pholidotus Zavortink, 1973. b An. (Ano.) calderoni. c An. (Ano.) pseudopunctipennis

Fig. 5

Thorax of An. (Ano.) calderoni, lateral aspect. Abbreviations: C-I, forecoxa; C-II, midcoxa; C-III, hindcoxa; Mam, mesepimeron; Mks, mesokatepisternum; MS, mesothoracic spiracle; Msm, mesomeron; Ppn, postpronotum; Scu, scutum; Stm, scutellum

Fig. 6

Thoraces of Anopheles, lateral aspects. a An. (Nys.) darlingi Root, 1926. b An. pholidotus

Fig. 7

Hindtarsomeres of Anopheles spp. females. a An. (Nys.) albimanus Wiedemann, 1820. b An. (Nys.) darlingi. c An. (Nys.) nuneztovari Gabaldon, 1940. d An. (Ker.) neivai Howard, Dyar & Knab, 1913. e An. (Ano.) malefactor Dyar & Knab, 1907. f An. (Ano.) costai da Fonseca & da Silva Ramos, 1940

Fig. 8

Nomenclature of wing veins and of pale and dark spots on the dorsal surface of Anopheles spp. wings. a An. triannulatus. Abbreviations: BP, basal plate; PHD, prehumeral dark; HP, humeral pale; HD, humeral dark; PSP, presector pale; PSD, presector dark; SP, sector pale; PRSD, proximal sector dark; ASP, accessory sector pale; SCD, subcostal dark; DSD, distal sector dark (when the ASP is missing, the composite dark spot is termed the SD, sector dark); SCP, subcostal pale; PD, preapical dark; PP, preapical pale; AD, apical dark; AP, apical pale. b An. neomaculipalpus Curry, 1931. Dark and pale spot names and abbreviations follow [19]. Spots are listed from left to right; those shown in panel a are followed by additional spots shown in panel b. Additional spots present in species of the Arribalzagia Series; subcostal vein ends in a AD, dark spot, SCD, subcostal dark in the middle of subcostal area. Spots basal to SCD are termed PRSCP, presubcostal pale and PRSCD, dark spots and those distal to it are the POSCP, postsubcostal pale and POSCD, dark spots. Also, in species of the series, the PP, preapical pale is interrupted by an ASD, accessory preapical dark

Fig. 9

Pale and dark wing spots in species of Anopheles (Nyssorhynchus). a An. braziliensis (Chagas, 1907). b An. albitarsis Lynch Arribálzaga, 1878. c An. strodei Root, 1926. d An. triannulatus (Neiva & Pinto, 1922). e An. nuneztovari. f An. albimanus

Fig. 10

Wings of species of Anopheles (Kerteszia). a An. pholidotus. b An. homunculus Komp, 1937. c An. gonzalezrinconesi Cova Garcia, Pulido F. & Escalante de Ugueto, 1977. d An. neivai

Fig. 11

Wings of species of Anopheles (Anopheles). a An. pseudopunctipennis. b An. calderoni. c An. peryassui Dyar & Knab, 1908. d An. mattogrossensis Lutz & Neiva, 1911

Fig. 12

Abdomens of Anopheles spp., dorsal view. a An. (Nys.) darlingi. b An. (Nys.) albimanus

Fig. 13

End of abdomen; tergum VIII of Anopheles spp., dorsal view. a An. (Ano.) peryassui. b An. (Ano.) mattogrossensis

Fig. 14

Abdominal sternum I, An. (Nys.) albitarsis