The austral-most record of the genus Haemagogus Williston (Diptera: Culicidae)

The genus Haemagogus Williston, 1896 includes numerous species of yellow fever virus vectors. Their immature stages are found mainly in tree holes, but they can also be found in artificial containers; the adults generally inhabit savannas, forests, and cultivated areas¹. To conduct control programs, it is necessary to know the distribution of mosquito species, mainly those with public health implications, which is essential to determine areas of potential risk of transmission of diseases². Haemagogus is restricted to North and middle of South America, Central America, and the Caribbean islands (from Jamaica to Martinique) with a single species recorded in the Nearctic, in Texas, USA. In South America, its distribution includes north to central regions of the subcontinent, from Venezuela to the north of Argentina, except for the Pacific coast of the Gulf of Guayaquil (Ecuador) and certain elevations of the Andes^3,4,5. There are some mosquito genera, such as Toxorhynchites, Orthopodomyia, Haemagogus, Limatus, Isostomyia, Onirion, Sabethes, Trichoprosopon, Wyeomyia, and certain subgenera of Anopheles, Aedes, and Culex, whose species exclusively use phytotelmata as breeding sites. Among the phytotelmata most used by mosquitoes are bamboo, tree holes, floral bracts such as woody phytotelmata, and herbaceous phytotelmata such as Apiaceae, Araceae, and Bromeliaceae⁶ while several of the species also do so in artificial containers. Among the species of Haemagogus, there is single record of phytotelmata on Prosopis, Prosopis juliflora as the breeding site of Haemagogus equinus⁷. In Argentina, 4 species are cited out of the 28 species described for the genus Haemagogus: Hg. (Con.) leococelaenus Dyar and Shannon, Hg. (Hag.) capricornii Lutz, Hg. (Hag.) janthinomys Dyar and Hg. (Hag.) spegazzinii Brèthes⁶. These species are specialists, that is, they use phytotelmata as their only breeding site, although only two species have been reported breeding in tree holes: Hg. leucocelaenus in Misiones and Hg. spegazzinii in Salta, Córdoba⁶, and Chaco⁸; in all cases, the host plants were not identified.

Hg. spegazzinii extends in South America from eastern and southeastern Brazil to Paraguay, northern Argentina, and eastern Bolivia and Ecuador, Venezuela³, and Colombia^9 *. In Argentina, its distribution covers the provinces of Catamarca, Chaco, Córdoba, Corrientes, Formosa, Jujuy, Salta, San Luis, Santa Fe, Santiago del Estero, Tucumán, Mendoza, and Misiones^8,10.

La Pampa province is located in the central region of Argentina. This province has an arid temperate weather with 300-850 mm of annual precipitation and annual temperatures ranging between 14 and 16 °C¹¹. One of the biogeographical provinces represented in the region is the Pampean province situated in the north-eastern region¹². Only 17 species of mosquitoes are cited, and none of them belong to Haemagogus¹³. In the present study, new distributional records are provided, and Prosopis caldenia is recorded as a new host plant to Haemagogus spegazzinii breeding sites.

One adult female mosquito was collected using hand-held aspirators on humans and was kept in a labeled plastic pot with cotton, paper, and naphthalene. Three mosquito larvae were collected by dipper and pipette, from a tree hole of Prosopis caldenia Burkart (Figure 1). Mosquitoes in the immature stages were kept in a labeled plastic bottle and brought to the laboratory for identification and reared up to one male and two females (Figure 2). Material obtained was identified based on morphological keys³. The abbreviations of genus and subgenus follow the approach of Reinert¹⁴.

FIGURE 1: Breeding site of Haemagogus spegazzinii in Prosopis caldenia. 

FIGURE 2: Photo of female Haemagogus spegazzinii. Scale bar: 10 mm. 

Material Examined: La Pampa, Eduardo Castex, 35° 50′ 24.82′′ S, 64° 31′ 50.23′′ W (Figure 3), Feb. 2016. One male, two females MLPDipC 4733 a and b, and 1 larva.

FIGURE 3: Map of the georeferenced point where Haemagogus spegazzinii was found. 

Liria & Navarro⁴ performed a study on the potential distribution of the species of Haemagogus and concluded that La Pampa could be a province of distribution of Hg. spegazzinii but with low occurrence probability. Despite this species being collected in La Pampa, climate conditions in that year were special with heavy rains registered between January and February 2016 (120 and 141.5 mm, respectively). Furthermore, collections during following years were nil. We think this could mean the population is not established in the region, but because we found larvae, it means they were able to develop in this location. Despite the species not being established in the province, a change in climate conditions could make it suitable for its establishment in the future. This implication is of great medical importance for the province and Argentina; it could mean a probable future extension of distribution of this yellow fever vector in the country.

Finally, in the present study, new distributional records are provided and Prosopis caldenia is recorded as a new host plant to Haemagogus spegazzinii breeding sites. This represents the first record of a species of Haemagogus and particularly of Hg. spegazzinii given that La Pampa, Argentina corresponds to the southernmost locality for species of the genus. With this registry, the number of species found in La Pampa province rises to 18.