Aedes cinereus Meigen

by Wayne J. Crans, Rutgers University

Subgenus: Aedes

Type of Life Cycle: Ochlerotatus canadensis Type (Univoltine Northern Aedes with limited egg hatch later in season)

Typical Habitat: Semi-permanent Bogs and Swamps

Larvae Present: Early Spring, with lesser numbers after heavy rains in late summer and fall

Head Hairs:

Upper: 5-9 branched

Lower: 4-8 branched

Antenna:

Length: Slightly more than ½ as long as head

Tuft: Inserted before middle of shaft

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

Comb Scales: Irregular double row

Siphon:

Index: 4.0-4.5

Tuft: 3-5 Hairs, very small

Pecten: 1-3 teeth detached

Anal Segment:

Saddle: Incomplete

Precratal tufts: 3-4

Other: 1) Upper, lower & pre-antennal hairs inserted in a diagonal straight line 2) Much smaller than other species of Aedes in the habitat

GEOGRAPHIC DISTRIBUTION: Aedes cinereus has a distribution that includes all of the mainland states with the exception of the arid southwest. The mosquito is widely distributed in New Jersey with records from nearly all of the counties. The species reaches greatest numbers in the northern counties during early spring. Light trap records indicate that the mosquito is present in low numbers in many areas of the coastal plain in southern New Jersey. In all probability, Ae. cinereus larvae are sparsely distributed throughout the pinelands of southern New Jersey wherever suitable habitat is present.

SEASONAL DISTRIBUTION: Aedes cinereus is a univoltine species that hatches in greatest numbers during the month of April. Collection records from northern New Jersey show that early instar larvae appear during the 2nd or 3rd week of April in most areas. Egg hatch is staggered, however, and specimens can be collected well into the month of May. The species frequently re-appears during the summer and relatively large populations can be found following heavy rains in August and September. Collection records from the southern half of the state are sparse and the mosquito's true seasonal distribution is unclear in that area. Light trap records from southern New Jersey document a spring population, but very few specimens have been collected beyond the month of June on the coastal plain.

LARVAL HABITAT: Aedes cinereus is an opportunistic species that can be found in a very wide range of larval habitats. The species is most frequently found in permanent and semi-permanent bogs but collections can also be made from a variety of floodwater habitats. During the early part of the season, Ae. cinereus is common in cattail swamps and the species is frequently collected with Oc. abserratus. In semi-permanent swamps that are located within wooded habitats, Ae. cinereus associates with Cs. morsitans. Throughout the early season, Ae. cinereus may be mixed with Ae. canadensis in a variety of transient water situations. As the season advances, Ae. cinereus can occur with many of the summer floodwater mosquitoes.

COMMON ASSOCIATE SPECIES: Oc. abserratus, Ae. canadensis, Ae. vexans, Ae. fitchii, Cs. morsitans, An. walkeri

LARVAL COLLECTION: Aedes cinereus can easily be overlooked in larval collections because of its small size. The species is frequently mixed with much larger early season Aedes and the smaller specimens can be mistaken for early instars that require further rearing for accurate identification. A 4th instar Ae. cinereus larva is about the same size as an early 3rd instar Ae. canadensis. If the specimens are not critically examined, they may be mistaken for earlier instars of the dominant species in the collection.

Aedes cinereus larvae tend to aggregate within dense stands of aquatic vegetation and placing the dipper close to any emergent vegetation in the habitat enhances the chances of collecting this species. In semi-permanent woodland pools, Ae. cinereus can be collected from clumps of Carex by pushing the dipper into the dead grass mat surrounding the plant and drawing water from the inner recesses of the vegetation. In pools that support little emergent vegetation, the larvae often hide under leaves very close to the edge. Cattail appears to be a preferred plant and Ae. cinereus larvae can be collected with relative ease as long as the dips are taken close to the plants. The species is rarely collected from open water in any of the numerous habitats that it occupies during the early spring.

LARVAL IDENTIFICATION: Aedes cinereus larvae are easy to recognize as preserved specimens. The air tube is relatively long for an Aedes and the pecten extend well beyond the mid-point. The separated pecten teeth toward the apex of the siphon are especially characteristic. The siphonal tuft is very small and may appear to be missing at low magnification. The comb scales appear as an irregular double row. The head hairs, however, provide the diagnostic character that is used to separate the species in most keys. All mosquito larvae have paired upper, lower and pre-antennal head hairs. In most cases, the upper head hairs are centrally located on the head capsule and the lower head hairs are inserted at a point well below toward the mouth opening. The pre-antennal head hairs are normally off to the side with their insertion point very close to the base of the antennae. In most Aedes, an imaginary line drawn from the upper head hair to the pre-antennal head hair would miss the insertion point of the lower head hair because of its forward position on the head capsule. In Ae. cinereus, the upper, lower and pre-antennal hairs occur on a perfect diagonal and a line drawn from the upper to the pre-antennal would pass through the insertion points of all three.

REPRESENTATIVE COLLECTION RECORDS

Northern New Jersey

Location: Hackettstown, Warren Co.

Date : April 21

Habitat : Semi-permanent pool in deep woods

Collected from emergent vegetation

Instar : 4th (Mixed with Cs. morstans)

Central New Jersey

Location: Great Swamp National Wildlife Refuge, Morris Co.

Date : May 9

Habitat : Cattail Swamp

Instar : 4th & Pupae

IMPORTANCE: Aedes cinereus rarely occurs in large numbers by itself but the mosquito can be an aggressive biter. The species does not fly far from its larval habitat and, therefore, functions primarily as a local pest. Aedes cinereus is a woodland species that will bite any time during the day. The mosquito is known as an ankle biter because it usually focuses its feeding activities toward the lower extremities of the body. This is one of the few woodland Aedes that does not swarm about the head when you enter its habitat. The bite frequently goes unnoticed because its attacks on the lower half of the body are overshadowed by other species that are flying for the face.