Approximately 60 species of the genus Coquillettidia Dyar are known worldwide. However, the only species of Coquillettidia that occurs in the USA and Canada is the so-called cattail mosquito, Coquillettidia perturbans (Walker) (Figure 1) (Burkett-Cadena 2013). This particular mosquito is a permanent freshwater species whose larvae and pupae exhibit the unusual habit of attaching to the roots of emergent aquatic plants, especially cattails (hence the suggested common name) (Morris et al. 1990). The biting females can be a nuisance to domestic animals and humans when abundant because they are persistent and painful biters (Burkett-Cadena 2013). The cattail mosquito is a vector of several important disease-causing organisms that affect humans. It is active principally during the early evening hours, but is known to seek humans for blood meals during the day in shady places where adult mosquitoes are resting (Carpenter and LaCasse 1955; WRBU 2016).
Coquillettidia perturbans (Walker 1856)—accepted name
Mansonia (Coquillettidia) perturbans (Walker 1856)
Culex perturbans (Walker 1856)
Culex testaceus (Wulp, 1867)
Culex ochropus (Dyar and Knab, 1907)
Coquillettidia perturbans occurs throughout portions of Canada, the United States, and Mexico (Carpenter and LaCasse 1955; WRBU 2016). It is a widely distributed across the eastern half of the US, southern Canada and several areas in the western US (Figure 2, Burkett-Cadena 2013).
Eggs are laid on the surface of the water near emergent vegetation (Carpenter and LaCasse 1955). They are elongate and white in color initially but darken within one to two hours after being laid. Females attach individual eggs together as they are deposited to form a floating raft (Figure 3) (Carpenter and LaCasse 1955; Crisp et al. 2002).
Mature larvae are grayish white in color and have long, whip-like antennae, each bearing a large, branched seta (Figure 4 Burkett-Cadena 2013). The head is much wider than it is long, and the comb on the eighth abdominal segment has 8–15 thorn-shaped scales. Unlike most mosquitoes that obtain oxygen at the water surface via the siphon (air tube), larvae of Coquillettidia perturbans have a heavily sclerotized siphon that resembles a short, pointed saw. The saw-like projections are used to pierce the hollow roots or submersed plant stems (especially cattails (Typha spp.) ) and other aquatic plants for respiration (Figures 4 and 5) (Carpenter and LaCasse 1955; Burkett-Cadena 2013).
Pupae are a non-feeding transitional stage in which the adults complete their development (Figure 4). There are two body regions in the pupal stage, an expanded cephalothorax (fused head and thorax) and an elongated abdomen with eight movable segments terminating in a pair of paddles (Crisp et al. 2002). Two short, flared tubules (trumpets) projecting from the cephalothorax surround the openings to the respiratory system. Pupae of Coquillettidia perturbans insert their pointed trumpets into the hollow, air-filled roots or submersed stems of cattails and other aquatic plants to obtain oxygen.
Adults are medium-sized mosquitoes with a "salt and pepper" appearance due to the the body being covered inpatches of white, black, and brown scales (Figure 1 and 6). The proboscis (tubular mouthparts) is dark scaled with a median band of pale white scales. The dorsal surface of the thorax has golden brown scales. The abdomen in females is bluntly rounded, and mostly dark scaled with lateral patches of pale scales on each segment. Tarsomere 1 (foot segment) of each leg has a basal and median band of pale scales (Figures 1 and 6). The wing veins are covered with intermixed dark and light broad scales (Burkett-Cadena 2013).
Life Cycle and Biology
Females deposit 150–350 eggs on or near the leaves of aquatic plants (Smith and McIver 1984), particularly cattails. First-instar (newly hatched) larvae seek out and attach themselves to the roots or submersed stems of aquatic plants where they remain to complete their development (Carpenter and LaCasse 1955). However, larvae can readily detach and burrow into the sediment if disturbed (Darsie and Hutchinson 2009). They do not need to rise to the surface of the water to breathe like most other mosquito larvae do, because they obtain oxygen directly from the plant. The larval stage has four instars, the durations of which vary greatly depending upon temperature, latitude, and food availability (Lounibos and Escher 1983). Bacteria, particulates, protozoa and algae were found to comprise the majority of particulate food ingested by the cattail mosquito (Merritt et al. 1990). The cattail mosquito undergoes an obligatory diapause in the larval stage (Morris et al. 1986). In the northern parts of its range, it overwinters as immature or mature larvae; synchronous emergence of adults generally occurs the following spring or early summer (Carpenter and LaCasse 1955; Lewis and Bennett 1980).
In Florida, adults can be encountered year-round but peak abundance occurs from June through September (Burkett-Cadena 2013). In Canada, the Coquillettidia perturbans exhibits a univoltine (one generation) life cycle; the larval stage can last up to nine months (Lewis and Bennett 1980; Allan et al. 1981). In contrast, there are two or three broadly overlapping generations in central Florida (Lounibos and Escher 1983; Morris et al. 1986). The pupal stage is quite variable, lasting up to several weeks. After adults emerge from the pupal stage, the wings will harden within 24 hours, and they will be able to fly soon thereafter (Mullen and Durden 2009). The sex ratio of males and females is approximately 1:1. The life span of the adult is approximately one to two months with females tending to outlive their male counterparts.
Although mainly associated with cattails (Typha spp.), larvae and pupae of Coquillettidia perturbans are found in association with the roots or submersed stems of many different aquatic plants, including arrowhead (Sagittaria spp.), pickerelweed (Pontederia spp.), water lily (Nymphaea spp.), rushes (Juncus spp.), reeds (Phragmites spp.), sedges (Carex spp.), and water arum (Calla spp.) (Morris et al. 1986). All of these host plants are rooted in thick humus-rich hydric soils.
Males feed exclusively on flower nectars (Figure 7) and other plant juices. Females also feed on flower nectar for nutrition, but feed on blood of vertebrate animals, which is essential for egg production (Figure 6). Females of Coquillettidia perturbans have been reported to bite and feed on the blood of a wide variety of wild and domestic birds and mammals, including chickens, quail, cattle, rabbits, armadillos, raccoons, opossums, and humans (Edman 1971).
Females of Coquillettidia perturbans are vicious biters, capable of penetrating clothing. They also are strong fliers, able to travel up to five miles. In addition to being a nuisance due to their biting behavior, this mosquito is known to transmit two major arboviruses, West Nile virus and eastern equine encephalomyelitis virus (Darsie and Hutchinson 1990; CDC WNV 2015). Although there are equine vaccines for these viruses, currently there are no vaccines available for humans. Protective clothing and mosquito repellent should be used when outdoors to avoid mosquito bites (ENY-671, https://edis.ifas.ufl.edu/in419).
Because larvae and pupae of Coquillettidia and Mansonia mosquitoes do not need to breathe at the water surface, they are difficult to control with conventional larvicides. Immature stages can be sampled by pulling up aquatic plants (cattails, sedges, pickerelweed, etc.), washing them in a white pan of water, and examining the sediment and debris for the presence of larvae or pupae (Dame and Fasulo 2002; MMCA 2002). Cattails (Typha spp.) are native aquatic plants that can exhibit invasive characteristics in disturbed wetlands. Because they are the preferred developmental host of Coquillettidia perturbans (Walker), removal of excessive cattail growth (source reduction) often is the only effective and economical long-term method of management.
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