A single female specimen of Aedeomyia squamipennis (Lynch Arribalzaga) was collected and identified in Monroe County, FL, during routine weekly adult surveillance on October 14, 2021. Florida Keys Mosquito Control District's (FKMCD) weekly surveillance utilizes a solid carbon dioxide/dry ice (CO₂)–baited Centers for Disease Control and Prevention (CDC) miniature light trap (Model 512; John W. Hock, Gainesville, FL) set for an approximately 24-h period. The collection site located on Cross Key has been monitored using CO₂-baited CDC light traps for 18 years. This is the first observation of Ad. squamipennis at this location (Fig. 1) and in the Florida Keys.

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One of 7 species in its genus, Ad. squamipennis is the only species of this genus found in the Americas (Dyar 1928). Six of the 7 species, including Ad. squamipennis, belong to the subgenus Aedeomyia, and only Ae. furfurea (Enderlein) belongs to the subgenus Lepiothauma. Aedeomyia squamipennis is a tropical species whose natural range extends from Mexico to Argentina (Heinemann and Belkin 1977, 1979). In recent years, Ad. squamipennis has been found outside its Central–South American range, including mainland Florida (Burkett-Cadena and Blosser 2017), Cuba (Peraza Cuesta et al. 2015), and Hispaniola (Dominican Republic) (Pena and Chadee 2004). Since it is a new species to the USA, no identification guides were readily accessible at FKMCD, so an identification guide from Australia was used to identify the genus (GWADOH 2021). Positive identification of Ad. squamipennis can be made with identification keys by Belkin et al. (1970) and Clark-Gil and Darsie (1983), but these were not used during initial observation. Further investigation and opportune timing of a visit to the Florida Medical Entomological Laboratory in Vero Beach, FL, provided species confirmation of the specimen (Burkett-Cadena and Blosser 2017; Burkett-Cadena, personal communication). Succinctly described by Burkett-Cadena and Blosser (2017), Ad. squamipennis is a medium-sized species and adult females are identified by short, thick antennal flagellomeres; wings covered in a striking pattern of broad white, yellow, and brown scales; absence of prespiracular and postspiracular setae; and an apical tuft of scales on the mid- and hind femora (Fig. 2A, 2B). Descriptions of both the males and larval forms of this species are also provided by Burkett-Cadena and Blosser (2017) but are not discussed in this text.

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The collection site on Cross Key (25.188579°N, 80.390503°W), colloquially called “Lois Ryan Road” by FKMCD staff, is a private road surrounded by tidal red (Rhizophora mangle L.) and black mangrove (Avicennia germinans L.) swamps. Associated catch included Aedes taeniorhynchus (Wiedemann), Ae. triseriatus (Say), Anopheles atropos Dyar and Knab, Culex nigripalpus Theobald, and Cx. bahamensis Dyar and Knab. Characterized by tidal saltwater and brackish water pockets, this swamp produces large populations of Ae. taeniorhynchus during the summer months and An. atropos during the fall and winter, and is most heavily populated during the wet summer months (Hribar 2002, 2021).

Aedeomyia squamipennis is typically associated with aquatic plants, particularly Pistia stratiotes (L.), Azolla sp., Salvania sp., Utricularia sp., and Eichhornia crassipes (Mart.) Solms (Tyson 1970), but most likely associated with Pistia spp., especially in southern Florida (Peterson and Linley 1995, Burkett-Cadena and Blosser 2017). These aquatic plants are not found in close proximity to the trap site and are also generally considered to be associated with freshwater, a habitat not provided by mangrove swamps or the Florida Keys topography. Additionally, Ad. squamipennis larvae have yet to be reported in tidal floodwater or brackish water. For these reasons, it is unlikely that this species will become established in the Florida Keys.

Wind speed and direction in the week leading up to this novel collection varied between 12.1 and 21.6 mph, with wind gusts up to 60 mph and wind direction ranging from 57° to 146° (ENE–SE) (Visual Crossing 2022). This highly variable wind speed and direction indicate that wind-driven migration may have brought Ad. squamipennis from the Everglades National Park in mainland Florida approximately 6 mi north of the trap site, where associated freshwater aquatic plants are more abundant. Although wind-driven migration is a possible explanation for this collection, so too is population expansion. The collection site is located 16.6 mi southeast of the initial collection made in 2017, suggesting that Ad. squamipennis has migrated from its initial discovery locality and is expanding its range in South Florida. This species may have already established in mainland Monroe County, but FKMCD does not monitor mosquito populations outside the populated archipelago.

This novel species' presence in Florida carries with it a potential for introduction of arboviruses to the state. Studies have shown it to be a prominent carrier of Gamboa virus (GAMV) (Calisher et al. 1981, Mitchell et al. 1985), and vertical transmission of GAMV by Ad. squamipennis has been seen in the field (Dutary et al. 1989). Field-collected specimens have also been shown to carry avian malaria (Plasmodium spp.) (Gager et al. 2008) and Venezuelan equine encephalitis virus (Mitchell et al. 1985). This species has the potential to become an important vector of these pathogens in mainland Florida, but it is unlikely that it will become an important vector in the Florida Keys.