Culex salinarius Coquillett

by Wayne J. Crans, Rutgers University


Subgenus : Culex

Type of Life Cycle : Model for Culex salinarius Type, multivoltine Culex with some salt tolerance

Typical Habitat : Brackish water swamps

Larvae Present : Late Spring to Fall

Head Hairs:

Upper: Multiple

Lower : Multiple

Antenna:

Length: Shorter than head, constricted

Tuft: Large, multiple, inserted at constriction

Abdominal Hairs (Segments III-VI) : 2-2-2-2 (Possibly triple on some segments)

Comb Scales : Many scales in a patch

Siphon:

Index: 6.5 - 7.0

Tufts: 4-5, paired 2-4 branched tufts inserted beyond pecten

Pecten: 10-16 teeth on basal 1/4 of siphon

Anal Segment:

Saddle: Complete ring

Precratal tufts: None

Other:  1) Gill length can be variable; 2) Siphonal Index fairly diagnostic

 

GEOGRAPHIC DISTRIBUTION: Culex salinarius has a distribution that extends over most of the eastern United States from Maine south to southern Florida, west to central Texas and north to the lower Great Lakes region.  Relict populations have been reported in the west from New Mexico, Wyoming and Idaho.  The mosquito is susceptible to extreme cold and is frequently killed off by severe winters in the northern limits of its range.   Repopulation of northern habitats is thought to take place by migration where the species persists until the next killing temperatures are encountered.  Culex salinarius has been reported from every county in New Jersey but reaches greatest abundance in coastal areas near freshwater impoundments.

 

SEASONAL DISTRIBUTION: Culex salinarius has a life cycle similar to Culex pipiens with several notable exceptions.  The mosquito enters hibernation in late fall but does not congregate in dwellings like the common House Mosquito.  Hibernation is thought to take place in natural shelters with muskrat huts and animal burrows cited as likely overwintering habitat.  Culex salinarius does not produce large amounts of fat body and does not diapause in a torpor like Cx. pipiens.  Adult Cx. salinarius host seek well into the fall and often pester hunters in duck blinds during the month of November.  The females can become active at the first sign of mild weather and may actively seek a blood meal during the January thaw. Light traps operated year round in Ocean Co. NJ captured a least 1 female Cx. salinarius every month during winter.  The species is multivoltine, like most Culex, and populations build gradually from spring through summer.  There is generally a late season population peak in the fall which persists until cold weather forces the adults into hibernation.  Larval populations build markedly toward the end of summer and larvae are frequently found in atypical habitats late in the season.

LARVAL HABITAT: Culex salinarius is often referred to as the “Salt Marsh Culex” but larvae rarely occur in numbers on the open salt marsh.  The mosquito does have salt tolerance but is capable of breeding in purely fresh water.  The larvae are particularly abundant in freshwater impoundments, especially impoundments where salt marsh habitat has been reclaimed through dyking and flooding from upland runoff.  Culex salinarius populations peak immediately after flooding because the rotting saltmarsh vegetation creates an infusion that functions as an oviposition attractant.  Virtually any freshwater habitat with dying vegetation can support Cx. salinarius larvae.  In coastal areas, the mosquito frequently invades pools of open water in Atlantic White Cedar swamps late in the season directly above the subterranean crypts that support Culiseta melanura.  When Cx. salinarius does occur on the salt marsh it is generally limited to the upper edges where brackish, rather than saline conditions are found.  Flooded stands of Phragmites frequently produce Cx. salinarius in numbers.  Roadside ditches, moderately polluted groundwater and artificial containers provide secondary larval habitat, particularly at inland foci where the species is less abundant.

COMMON ASSOCIATE SPECIES: An. bradleyi, Cx. restuans, Ae. cantator

LARVAL COLLECTION: Culex salinarius larvae can usually be collected in numbers from densely vegetated areas of freshwater impoundments.  This is a permanent water breeder that reaches greatest abundance in habitats that have remained flooded all summer long.  Larval populations are usually highest late in the summer in areas devoid of predacious fish.  Collection may be difficult because the species is frequently associated with unstable substrates.  Permanently flooded dredge spoil sites along the Delaware River produce huge populations of this species but are virtually impossible to sample over most of their area. 

LARVAL IDENTIFICATION: Culex salinarius is fairly easy to recognize in the larval stage because of the exceptionally long, thin air tube.  The species superficially resembles Culiseta melanura but usually occurs in very different habitat.  Under the microscope, the comb scales of Cx. salinarius occur as a patch and are very different from the barred comb scales of Cs. melanura.  The scattered siphonal tufts of Cx. salinarius also distinguish it from either Cs. melanura or Cx. territans.   Culex salinarius closely resembles Cx. pipiens and may be collected together with that species.  Accurate measurement of siphonal index is the best method of separating these 2 similar species.

 

REPRESENTATIVE COLLECTION RECORDS

Northern New Jersey

Location: Hackensack Meadowlands, Bergen Co.

Date:  August 3

Habitat: Semi-polluted Freshwater Impoundment

Instar : All instars

 

Southern New Jersey

Location: Canton Drain, Salem Co.

Date  July 28

Habitat : Freshwater Impoundment

Instar  : All instars

 

IMPORTANCE: Culex salinarius is a mosquito species that accepts birds as well as mammals.  As a result, it has been incriminated as a potential bridge vector of the encephalitis viruses.  Virus isolations have been made from wild populations but are a fairly rare occurrence.  Laboratory studies suggest that the mosquito has an extremely high threshold of infection and probably only functions as a secondary vector during epizootic episodes.  Culex salinarius can be a severe biting pest and readily enters houses to find a blood meal.  Culex salinarius can occur in unbelievably high numbers in coastal areas where suitable habitat is common.  Unlike Aedes sollicitans, this species rarely  causes nuisance during daylight hours.  Hugh swarms have been reported at twilight near brackish water habitat when the species emerges from its daytime resting sites in cattail and Phragmites.  Much of the adult control directed toward Aedes sollicitans in salt marsh areas help manage pest populations of this species as well.

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