Culex coronator: A New Species Record For Monroe County, Florida

Three collections of adult female Culex coronator Dyar and Knab have been identified from 3 separate locations in Monroe County, FL (Fig. 1), between July 21 and August 5, 2021. Two collections were made with solid carbon dioxide/dry ice (CO₂)–baited Centers for Disease Control and Prevention (CDC) miniature light traps Model 512 (John W. Hock, Gainesville, FL), and a 3rd collection was made using a CO₂ and BG-lure–baited Biogents Sentinel-2 (BG-2) (Biogents USA, Moorefield, WV) trap. Each trap was set for approximately 24 h during Florida Keys Mosquito Control District's (FKMCD) routine weekly adult surveillance program.

In southern Florida, the similarities between adult Cx. coronator and Cx. bahamensis Dyar and Knab adults make it difficult to differentiate these species when scales and notable characteristics are missing. Both species are medium sized, brown and white scaled, and have basal abdominal banding as well as pale banding on the hind tarsi; the tarsal banding being an uncommon characteristic in South Florida's Culex species. Culex coronator has a medial patch of pale scales on the underside of the proboscis, distinct from the complete medial pale band seen on the proboscis of Cx. bahamensis. Tarsal banding and ventral abdominal scale patterns were used as additional identifiers as described by Darsie and Ward (2005) and Burkett-Cadena (2013) when possible. Since Cx. bahamensis has been a common species in FKMCD adult surveillance trap data for years, it is unknown whether the resemblance to Cx. bahamensis has been overlooked in the past, or if Cx. coronator has only recently been introduced into the Florida Keys.

One adult female specimen was initially collected on Upper Matecumbe Key, FL (24.921828°N, 80.628787°W), in a CDC CO₂-baited light trap on July 21, 2021, along with Aedes taeniorhynchus Weid., Ae. aegypti (L.), Ae. tortilis Theobald, Cx. bahamensis, Cx. nigripalpus Theobald, Deinocerites cancer Theobald, and Wyeomyia vanduzeei Dyar and Knab in a tidal black mangrove swamp, spotted with solution holes and man-made mosquito ditches that remain inundated most of the year. A 2nd female specimen was collected by a CDC CO₂-baited light trap on Windley Key, FL (24.950092°N, 80.596527°W), on July 28, 2021, at the Windley Key Fossil Reef Geological State Park, a former limestone quarry. This site is characterized by tidal black mangrove (Avicenna germinans L.) swamps, solution holes, and rock holes as well as red mangrove (Rhizophora mangle L.) swamps nearby. Species collected with Cx. coronator included Ae. taeniorhynchus, Ae. tortilis, Anopheles atropos Dyar and Knab, Cx. bahamensis, Cx. quinquefasciatus Say, Cx. nigripalpus, and De. cancer.

Most recently on August 3, 2021, a female Cx. coronator adult was identified from a BG Sentinel-2 collection bag set in a residential neighborhood of Key Largo, FL (25.141546°N, 80.395440°W). Associated catch included Ae. aegypti, Ae. taeniorhynchus, and An. atropos. This collection site is not considered to be located near a natural breeding habitat. Although migration from a natural habitat is possible, the larval habitat of Cx. coronator varies widely from natural or man-made bodies of water to artificial containers (Najera-Vazquez et al. 2004, Goddard et al. 2006, Yee and Skiff 2014, Goddard et al. 2017) and indicates Cx. coronator is likely opportunistic in choosing oviposition sites.

Since Cx. coronator was first identified in the panhandle of Florida in 2005, it has expanded its range and has since been identified in every county in Florida except for Monroe County (Smith et al. 2006, Connelly et al. 2016, Sames et al. 2021). Its nonnative range now extends as far north as Memphis, TN (Trimm et al. 2017); Suffolk, VA, on the east coast (Akaratovic and Kiser 2017); and Enid, OK, in the Midwest (Bradt et al. 2019). The natural range of Cx. coronator reaches as far south as Argentina, but its presence in the northern Caribbean islands is only known by its recent discovery in Camagüey, Cuba (Almirón and Brewer 1996, Diéguez-Fernández et al. 2020). Currently, there are areas in the southeastern USA where Cx. coronator has not been identified although adjacent counties or states have collected the species for years. These data gaps are likely due to minimal or nonexistent mosquito surveillance programs or the inability to distinguish it from other adult Culex specimens.

Culex coronator is not currently considered a vector of medical importance, but studies have previously isolated St. Louis virus (Aitken et al. 1964), West Nile virus (Mackay et al. 2008, Unlu et al. 2010), and Zika virus (Elizondo-Quiroga et al. 2018) from infected individuals in their respective field collections. Although Cx. coronator prefers mammalian blood hosts (Mackay et al. 2010), it is likely an opportunistic feeder as noted by Mann et al. (2020), who reported Cx. coronator taking blood meals from several avian hosts.

Identifying adult specimens on 3 islands provides an indication that this species can potentially establish itself in the northern islands of the Florida Keys. However, larval specimens are yet to be found and adult collections span only 2 wk so the prevalence of Cx. coronator is currently undetermined. It is possible that Cx. coronator has been established in the northernmost portion of Monroe County, located on the southwestern portion of the Floridian peninsula in Everglades National Park. However, FKMCD does not conduct surveillance in the Everglades, and only monitors adult mosquito populations along the populated archipelago of the Florida Keys. Proper identification and continual adult mosquito surveillance collections will provide further indications of Cx. coronator's prevalence in the Florida Keys.