by Wayne J. Crans, Rutgers University
Subgenus: Ochlerotatus
Type of Life Cycle: Univoltine Northern Aedes (with limited egg hatch later in the season)
Typical Habitat: Any early season transient water
Larvae Present: Early Spring with lesser numbers following heavy rains in Summer and Fall
Head Hairs:
Upper: 4-9 branched
Lower: 4-8 branched
Antenna:
Length: Half as long as head
Tuft: Inserted before middle of shaft
Abdominal Hairs (Segments III-VI): 2-2-2-1
Comb Scales: Patch
Siphon:
Index : 3.0 - 4.0
Tuft : 3-8 branched
Pecten : Evenly spaced
Anal Segment:
Saddle : Incomplete
Precratal tufts : 2
GEOGRAPHIC DISTRIBUTION: Aedes canadensis has a distribution that extends from Labrador south to northern Florida along the Atlantic seaboard and west through Canada into Alaska. The mosquito is common in every state east of the Mississippi River, is well distributed in the central plains but is not found along the Pacific coast or the arid southwest. Most authors consider northern populations as a separate subspecies, Ae. canadensis canadensis. A darker form of this species, Ae. canadensis mathesoni cohabits the southeastern portion of its range. Aedes canadensis is New Jersey's most abundant early season mosquito and is common in every county of the state
SEASONAL DISTRIBUTION: Aedes canadensis larvae hatch from overwintering eggs during the early spring. In the southern half of the state, larvae can be abundant by early March. In more northern areas, Ae. canadensis appears after the true snow pool species and larvae may not be evident until late April. Small numbers of Ae. canadensis larvae frequently hatch during winter thaws in southern New Jersey and it is not uncommon to find 2nd instar larvae in arrested development more than a month before the major hatch occurs. Egg hatch is staggered with this species and fresh cohorts of larvae appear in typical habitat throughout the month of May. Although the species is considered univoltine, summer rains may produce repeated minor hatches of this species. In some years, rainfall during the hurricane season produces a major fall brood.
LARVAL HABITAT: Virtually any early season transient water in New Jersey will support Ae. canadensis larvae. The species is most common in shallow, leaf-lined pools in wooded areas but specimens will be encountered in deep snow pools, roadside ditches, vernal pools in open fields, along the edges of permanent swamps, and in acid water bogs. During the early spring, the species is most frequently mixed with Ae. stimulans, Ae. grossbecki and Ae. excrucians. Somewhat later in the season, the species shares habitat with Ae. cinereus, Ae. sticticus and Ae. vexans. Classic woodland pools form the predominant habitat for this species in the northern portion of New Jersey. Further south, the species is frequently encountered in bog habitats but is still most abundant in the dark water that is so characteristic of woodland pools throughout the pine barrens region. Late season populations of Ae. canadensis may be mixed with Ae. vexans, Aedes atlanticus and Psorophora. ferox in woodland pool habitats that reflood following exceptionally heavy rainfall.
COMMON ASSOCIATE SPECIES: Ae. stimulans, Ae. grossbeckii, Ae. excrucians, Ae. cinereus, Ae. vexans
LARVAL COLLECTION: Aedes canadensis larvae are so numerous during early spring that no special collection techniques are needed to locate the species. In most cases, spring collections will be dominated by this abundant early season mosquito. Rare species may be overlooked because of the repeated occurrence of this mosquito over such a wide range of habitats. It generally pays to collect large numbers of larvae from typical habitat and place them in a white pan at the field site for sorting purposes. Larvae that appear atypical because of size, color or behavior can be placed in separate vials for closer examination in the laboratory. This eliminates sorting through large numbers of the common species to find the isolated rare specimen. As the season advances, Ae. canadensis larvae become more secretive and more difficult to collect. The larvae tend to hide beneath leaf litter on the bottom of the pools during the month of May and casual dipping can miss the species even though large numbers may be present.
LARVAL IDENTIFICATION: Aedes canadensis larvae are easily separated from other spring Aedes by the combination of multiple upper and lower head hairs, incomplete saddle and evenly spaced pecten teeth. Care, however, should be taken to scan all specimens in a typical collection for these basic characteristics if you have not screened the sample for atypical larvae at the field site. Aedes canadensis is dominant in numerous early season habitats. Rare species (e.g. Ae. punctor, Ae. intrudens etc.) can be overlooked because of the more numerous Ae. canadensis larvae. Species such as Ae. stimulans, Ae. grossbecki and Ae. provocans may share habitat with Ae. canadensis during the early season but each of these species should be at least one instar ahead and evident because of their size. Aedes sticticus is a larva that may be collected with Ae. canadensis and is very easy to overlook. The saddle extends further around the anal segment in Ae. sticticus and is probably the best diagnostic character to separate these very similar larvae. It is best, however, to have knowns of each species available for comparison because the saddle characteristic is discretionary and most of the other characters shared by these two species overlap.
REPRESENTATIVE COLLECTION RECORDS
Northern New Jersey
Location: Wood Glen, Hunterdon Co.
Date: April 20
Habitat: Shallow Woodland Pool
Instar: 3rd & 4th
Central New Jersey
Location: Great Swamp, Morris Co.
Date: April 28
Habitat : Drainage Ditch
Instar: 4th & Pupae
Southern New Jersey
Location: Warren Glen, Ocean Co.
Date: April 12
Habitat: Cranberry Bog
Instar: 3rd & 4th
IMPORTANCE: Aedes canadensis can be a serious pest, especially in wooded areas close to its breeding habitat. The mosquito does not appear to range far but can be an aggressive biter in shaded areas. The mosquito appears to be extremely long lived and specimens are frequently collected nearly devoid of markings. The mosquito has been implicated as a vector of the California group viruses and has repeatedly been cited as an efficient vector of dog heartworm. Aedes canadensis feeds on a broad range of animals, including large and small mammals, birds and even reptiles. The mosquito has a particular affinity for turtles and is frequently seen in a cloud following a turtle that is crossing the road to lay its eggs during the month of May.