by Wayne J. Crans, Rutgers University
Subgenus: Ochlerotatus
Type of Life Cycle: Univoltine Northern Aedes
Typical Habitat: Deep Snowpools
Larvae Present: Very Early Spring,
Head Hairs:
Upper: Single (Occasionally double)
Lower: Single (Occasionally double)
Antenna:
Length: Shorter than head
Tuft: Inserted before middle of shaft
Abdominal Hairs (Segments III-VI): 2-2-2-2 or 2-2-2-1
Comb Scales: Patch
Siphon:
Index: 2.5-3.0
Tuft: 4-8 Hairs
Pecten: Evenly spaced
Anal Segment:
Saddle: Incomplete
Precratal tufts: 2-4
Other: The long, pointed gills frequently have a rusty color
GEOGRAPHIC DISTRIBUTION: Aedes communis is a true snowpool species that reaches greatest numbers north of New Jersey. The species is common throughout the northern United States and Canada into Alaska. Throughout its range, the species is associated with heavily forested areas at high elevations. Aedes communis is a major pest in the Adirondaks in New York State and the Pocono Mountain range in Pennsylvania. In New Jersey, suitable breeding habitat is limited to the highest elevations of Sussex County and a few areas in Passaic County during early spring.
SEASONAL DISTRIBUTION: Aedes communis is one of the earliest mosquitoes to appear in New Jersey. Larvae can often be collected in late March and most populations begin pupating during the 3rd week of April. In the northernmost areas of New Jersey where the species is found, Ae. communis larvae reach their 4th instar before Aedes canadensis eggs hatch. The species is also well ahead of Aedes stimulans and Aedes excrucians in pools where the 3 species coexist. On a statewide basis, Ae. communis pupation corresponds with that of Aedes grossbeckii populations from the southernmost portions of New Jersey.
LARVAL HABITAT: Aedes communis larvae are most common in deep snowpools filled with dark colored water in forested areas above elevations of 1500 ft. In most cases, Ae. communis is the only large mosquito in the pools although in some years, small numbers of another northern species, Aedes provocans, may be intermixed. Machlonyx midge larvae, fairy shrimp, spotted newts and wood frog tadpoles frequently share the habitat. Aedes excrucians breed in the same pools but are generally only in their 2nd instar when Ae. communis is pupating. Aedes communis larvae are particularly abundant in the numerous snowpools within High Point State Park. The Sunrise Mountain area of Stokes State Forest is another area that provides habitat for this northern mosquito species. Many of the pools utilized by this species have steep banks and are too deep to enter with hip boots. Larvae from shallower pools develop more rapidly and may pupate as early as the 2nd week of April.
COMMON ASSOCIATE SPECIES: Ae. excrucians, Ae. stimulans, Ae. provocans
LARVAL COLLECTION: The larvae of Ae. communis rarely congregate close to the banks of the deep pools that they inhabit. Oxygen requirements are minimal in this cold water habitat and the larvae usually remain below the surface at least several feet from the shoreline. Slowly moving the dipper below the water's surface provides a bright, white background to observe the aquatic life in the pool. The mosquito larvae, Machlonyx midge larvae and fairy shrimp that are feeding in the deeper recesses of the pool stand out clearly against the white background of the dipper. Subsurface larvae can be collected by slowly raising the dipper under swimming specimens. In most cases, the larvae sound when disturbed and swim directly into the body of the moving dipper. In shallower pools, filimentous algal mats can make collection difficult by tying up the subsurface dipper and disturbing the leaf litter. On bright, sunny days, late instar Ae. communis larvae congregate in tight masses near the water's surface. When this occurs, most of the larvae become concentrated in a relatively small portion of the pool. When the larvae exhibit this balling behavior, a single dip can yield as many as 1000 specimens.
LARVAL IDENTIFICATION: Aedes communis larvae resemble Ae. stimulans and confirmation of identification is difficult with living specimens. The two species occupy similar habitat, although Ae. stimulans are normally one or more instars behind in their development. Under the microscope, both species have either single or double head hairs, comb scales in a patch, evenly spaced pecten teeth and an incomplete saddle. The gills of Ae. communis larvae almost always have a characteristic rusty-red color which may be evident in the dipper. The gills retain their color after preservation but gills are fragile and more often than not, break off in preserved specimens. Most keys use the spicules on the saddle as the major character to separate these two species. Aedes stimulans has well developed spicules on the posterior portion of the saddle. The saddle of Ae. communis is almost smooth. Proper placement of the specimen, however, is essential to accurately assess the presence or absence of spicules. The spicules are tiny teeth that protrude from the saddle and, in most cases, cannot be seen by looking directly down on the saddle. If the specimen is positioned on a white background with the siphon pointing directly up, the spicules on the posterior margin of the saddle stand out as sharp little teeth. They are very obvious in Ae. stimulans and totally absent in Ae. communis. As a result, the posterior margin of the saddle is raggedly toothed in Ae. stimulans and completely smooth in Ae. communis. A number of spring Aedes have spicules on the saddle including, Ae. aurifer, Ae. fitchii. Ae. grossbeckii, Ae. implicatus and Ae. thibaulti.
REPRESENTATIVE COLLECTION RECORDS
Northern New Jersey
Location: Stokes State Forest, Sussex Co.
Date : April 14
Habitat : Snowpool on road between Steam Mill Campground and Sunrise Mt.
Instar : 4th
Northern New Jersey
Location: Highpoint State Park, Sussex Co.
Date : April 14
Habitat : Snowpools at top of Ridge Road
Instar : 4th & Pupae
IMPORTANCE: Although Ae. communis occurs in large numbers within its restricted range, the species is not regarded as a significant pest in New Jersey. The mosquito is limited to mountainous habitat in New Jersey where few homes exist. The adults do not fly far from the breeding sites and annoyance is most intense after dark. This mosquito host-seeks in May and few people are out of doors in Ae. communis habitat when the adults are most numerous. Aedes communis may play a role in the maintenance cycle of Jamestown Canyon virus. Virus isolations have been obtained from larvae suggesting transovarial transmission of this California group virus.