Aedes fitchii (Felt & Young)

by Wayne J. Crans, Rutgers University


Subgenus : Ochlerotatus

Type of Life Cycle : Univoltine Northern Aedes

Typical Habitat : Grassy roadside ditches, Cranberry bogs

Larvae Present : Early Spring

Head Hairs

Upper: 3-4 branched (Occasionally double)

Lower: Double or Triple (Occasionally single)

Antenna

Length: Half as long as head

Tuft: Multiple, Inserted near middle of shaft

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

Comb Scales : Patch

Siphon

Index: 4.5 - 5.0, Gradually tapered

Tuft: 3-8 Hairs

Pecten: Evenly spaced

Anal Segment

Saddle: Incomplete

Precratal tufts: 1-2

GEOGRAPHIC DISTRIBUTION: Aedes fitchii is a mosquito of the northern United States and Southern portion of Canada. Its range extends from Maine to New Jersey on the eastern seaboard, west to northern Nevada and north into British Columbia. The species has a scattered distribution throughout the northern counties of New Jersey. Surprisingly large populations have been detected in some areas of the Pine Barrens in the southern portion of the state.

SEASONAL DISTRIBUTION: Aedes fitchii is a univoltine species with a typical northern Aedes life cycle. In northern New Jersey, the single generation of eggs hatch in April and the larvae reach 4th instar during the early part of May. Egg hatch may be staggered during the early season and a variety of instars can be collected from different habitats in the same geographic area. In southern New Jersey, this species frequently hatches during January thaws and 2nd instar larvae may be collected in small numbers throughout February and March. Adults are on the wing in May , blood feed and deposit their eggs which do not hatch until the following spring.

LARVAL HABITAT: Aedes fitchii has been reported from a wide variety of habitats but the species is most common in semi-permanent bodies of water in open areas that support emergent vegetation. Aedes fitchii is more apt to be collected in swamp habitats than woodland pools in New Jersey but the literature indicates that the species has a range that spans both habitats. Roadside ditches that support emergent grasses are a common larval habitat in northern counties. Abandoned cranberry bogs provide typical habitat in southern New Jersey.

COMMON ASSOCIATE SPECIES: Ae. abserratus, Ae. canadensis, Ae. cinereus, Cs. morsitans

LARVAL COLLECTION: Aedes fitchii larvae spend a great deal of time resting on the bottom and can easily be overlooked if they are present in small numbers. Using the white surface of the dipper as a background to locate submerged larvae does not usually work with this species. The larvae do not swim at mid-level like most other early season species, thus, the dipper passes over most of the specimens. Some authors advocate submerging a white dipper into pools where the larvae are known to occur and holding it motionless for up to a minute. Aedes fitchii larvae are attracted to the white outline and frequently swim into the dipper and collect themselves. Most Ae. fitchii populations are mixed in with larger numbers of spring species. If you cannot locate pure populations, the best collection technique is to take large numbers of specimens and sort for the few Ae. fitchii that are present.

LARVAL IDENTIFICATION: Aedes fitchii larvae resemble Aedes excrucians and the two species theoretically can be taken from the same habitat. Both are large early season Aedes and stand out in the dipper because of the long, tapered air tube. The air tube of both species looks more like a Culex or Culiseta than an Aedes which typically have siphons less than half as long. Microscopic examination reveals evenly spaced pecten teeth in Ae. fitchii and separated pecten for Ae. excrucians. With the exception of Ae. thibaulti, a species found in a specialized habitat, no other species of Aedes in New Jersey have an air tube with similar dimensions.

REPRESENTATIVE COLLECTION RECORDS

Northern New Jersey

Location: Cranberry Lake, Sussex Co.

Date : May 12

Habitat : Semi-permanent roadside pool

Instar : 4th & Pupae

Southern New Jersey

Location: Warren Grove, Ocean Co.

Date : April 21

Habitat : Abandoned Cranberry Bogs

Instar : 4th

IMPORTANCE: Aedes fitchii functions as a pest mosquito in some of the more northern states. In New Jersey, the species is early season, relatively rare and has no known economic importance.

 


Center for Vector Biology