Rutgers School of Environmental and Biological Sciences [Dept. of Entomology]

Culiseta melanura (Coquillett)


by Wayne J. Crans, Rutgers University

 

Subgenus : Climacula

Type of Life Cycle : Model for Culiseta melanura Type

Typical Habitat : Underground crypts in acid water Swamps

Larvae Present : Year round

Head Hairs

Upper: Multiple

Lower : Single

Antenna

Length: As long as head

Tuft: Large, multiple, inserted in a notch on outer 1/4 of shaft

Abdominal Hairs (Segments III-VI) : 2-2-2-1

Comb Scales : Single Row of unique barlike scales

Siphon

Index: 6.0 - 7.0

Tufts: Very small pair of basal tufts, median row of 10-16 short, ventral tufts, 5-6 minute dorsolateral tufts

Pecten: Evenly spaced on basal 1/3 of siphon

Anal Segment

Saddle: Complete ring

Precratal tufts: 2

Other: 1) Barlike Comb scales are diagnostic

2) Basal siphonal tufts, very small and extremely difficult to see

 

GEOGRAPHIC DISTRIBUTION: Culiseta melanura has a distribution that extends from Maine and southern Quebec south to southern Florida, west to eastern Texas and north to the lower Great Lakes region. The mosquito is associated primarily with lowland swamps and is missing from the Appalachian mountain range. Culiseta melanura is most abundant on the coastal plain of southern New Jersey but specimens have been collected from every county in New Jersey except Hudson.

SEASONAL DISTRIBUTION: Culiseta melanura has a life cycle unlike any other mosquito in the northeast. The species is multivoltine, like most Culex, but overwinters as a larva rather than an adult. Egg rafts deposited late in the season, hatch in the underground crypts that are favored as an oviposition site by this species. Larval development is retarded by cold conditions and overwintering takes place in the 2nd, 3rd and 4th instars. The largest larvae pupate in April and adults from this cohort are on the wing by early May. The mosquito exhibits several population peaks during the summer, separated by approximately one month each. The last generation of adults deposits the eggs that produce the overwintering larvae. Eggs that hatch in late summer or early fall, presumably overwinter as 4th instar larvae. Eggs that hatch after water temperatures drop, pass the winter in earlier instars.

LARVAL HABITAT: Culiseta melanura favors acid water and is normally found in acid bogs with a pH of 5.0 or lower. Two primary habitats for this species are found in New Jersey. In coastal areas, the mosquito reaches greatest numbers in Atlantic White Cedar swamps. At inland foci, the mosquito is associated with swamps comprised mainly of Red Maple. In either case, the adults seek out passageways through the root mat of trees where the water table is highest and lay their eggs in underground crypts. The larvae develop in the dark confines of the subterranean breeding sites and frequently have no contact with standing water that is visible from the surface. In swamps where mature trees have fallen, larvae can be found in the darkest recesses up, under the canopy provided by the root ball. When rotted out stumps occur in the swamp, larvae may be present in the deepest hollows.

COMMON ASSOCIATE SPECIES: Ae. thibaulti, Cs. morsitans

LARVAL COLLECTION: Culiseta melanura larvae are most numerous in large Atlantic White Cedar swamps along the Atlantic coast and Delaware Bay shores of southern New Jersey. Alternate habitats include mature stands of Red Maple that remain flooded well into the summer. This species may be found anywhere that acid water conditions provide larval habitat. There is a cedar swamp behind the lookout tower at High Point, on the NY-NJ-PA line that produces sizable populations of Cs. melanura every year. Areas where beaver have created habitat may be productive in any area of the state if the forest has been flooded for more than 3 years. Dipping for Cs. melanura larvae is often time consuming and non-productive. The mosquito prefers the deepest recesses and most are not accessible with a standard pint dipper. Dipping as far back into the recess of a fallen tree may produce a few specimens. The water, however, is usually deep close to the upended root mat and the first dips cause enough disturbance to make the larvae sound. Similar habitat is usually hard to find, thus, much of the time spent collecting this species involves waiting for larvae to re-surface in the limited habitat available. Collecting in cedar swamps involves traversing small clumps of land that support young trees and open water that has a treacherous bottom. The larvae of Cs. melanura are not in the open water; they are located beneath the hummocks where the trees are growing. Most cedar swamp hummocks have holes through the root mat that provide access to the water beneath. The openings to these "crypts" may only be 1-3" in diameter. A dipper is too large to fit into the hole and a turkey baster is not long enough to reach the water. We have had success using a bilge pump which is normally used to bail water out of boats. By removing the valve and using the pump as a syringe, it is possible to suck up water, larvae and debris from the crypts. If you use the pump without removing the valve, the larvae will be filtered out of the sample. Sorting the sample can be extremely tedious in the interior of the swamp but the bilge pump will reach habitat where larvae occur.

LARVAL IDENTIFICATION: Culiseta melanura is one of the easiest mosquitoes to recognize in the larval stage. The long air tube and prominent antennae are recognizable in the dipper. Under the microscope, the unique barlike comb scales are diagnostic. No other larva has a comb that is even remotely similar. Most of the difficulty identifying this species involves keying it out to genus. Culiseta melanura lacks the prominent basal hair tufts on the siphon that are used as the final generic character for Culiseta. Close examination reveals 2-3 tiny hairs but individuals who are not familiar with the species miss the character and place the larva in the genus Culex where species identification is not possible. The first couplet of every Culex key should describe barlike comb scales to catch any Cs. melanura that were mistakenly identified as Culex.

REPRESENTATIVE COLLECTION RECORDS

Northern New Jersey

Location: High Point State Park, Sussex Co.

Date: May 1

Habitat: Base of uprooted tree in cedar swamp

Instar : 3rd & 4th

Central New Jersey

Location: Helmetta, Middlesex Co.

Date :June 7

Habitat : Rotted out stump in Sphagnum Bog

Instar : 1st - 4th & Pupae

Southern New Jersey

Location: Villas, Cape May Co.

Date April 2

Habitat : Base of fallen tree in Red Maple Swamp

Instar : 3rd & 4th

IMPORTANCE: Culiseta melanura is a mosquito species that is not attracted to mammals. It does its host seeking in the canopy and feeds almost entirely on birds. The mosquito is responsible for maintaining eastern equine encephalitis virus in bird populations and plays a significant vector role in that regard. Culiseta melanura initiates the infection in bird populations; other mosquito vectors are responsible for equine and human cases.

©2008 Rutgers, The State University of New Jersey.
Last modified: 18 March 2013, lreed@rci.rutgers.edu.

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