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.
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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