by Wayne J. Crans, Rutgers University
(Note: See also Morphological Comparisons of Aedes/Ochlerotatus species.)
Subgenus : Protomacleaya
Type of Life Cycle : Multivoltine Aedes
Typical Habitat : Discarded Tire, Treehole
Larvae Present : All Season
Upper: Single (Rarely double)
Lower : 2-4 branched
Length: Half as long as head
Tuft: Single, very short, inserted at middle of shaft
Abdominal Hairs (Segments III-VI) : 2-2-2-2
Comb Scales : Single, irregular row
Index: 2.5 - 3.0
Tuft: 1-2 Short, Sparse Hairs
Pecten: Evenly Spaced
Precratal tufts: 2-3
Other : 1) Dorsal pair of gills longer than ventral pair
2) Lateral hair of saddle multiple
GEOGRAPHIC DISTRIBUTION: Aedes triseriatus is a mosquito of the eastern United States and extreme southern portion of eastern Canada. Its range extends from New Brunswick south to the Florida Keys, west to central Texas and north to the lower Great Lakes region. The mosquito occurs in a wide range of container habitats and can be found in urban as well as rural areas. Aedes triseriatus is common in every county of New Jersey.
SEASONAL DISTRIBUTION: Aedes triseriatus is a container breeding multivoltine Aedes that overwinters in the egg stage. The number of generations in a given area depends on the frequency of floodings during the breeding season. The species lays its eggs above the water line inside treeholes and artificial containers. Rainfall raises the water level in the container and floods the band of eggs left behind by females from previous generations. The overwintering eggs of Ae. triseriatus do not normally hatch until May but containers in direct sun may contain larvae much earlier in the season. Fluctuations in water level and staggered egg hatch produces overlapping generations of mixed larval instars. The eggs of this species enter diapause in September and larvae are rarely encountered in numbers beyond October 1. A few larvae, caught by cold conditions, often lag behind and eventually succumb to freezing temperatures.
LARVAL HABITAT: Aedes triseriatus is an opportunistic container breeder that utilizes artificial as well as natural container habitats. Cavities in a wide variety of tree species serve as primary habitat for this species in forested areas. The mosquito also lays its eggs in an array of artificial containers ranging from buckets, cans and barrels to discarded tires which represent the most common larval habitat for this species in New Jersey. The mosquito prefers aged habitat water containing leaf litter that produces tannins. The larvae are negatively phototrophic and congregate in the darker sections of the larval habitat. Tires in open areas contain fewer specimens than tires that are located in shade. Tire piles in forested habitats produce tremendous numbers of Aedes triseriatus, together with lesser numbers of associate treehole species.
COMMON ASSOCIATE SPECIES: Aedes triseriatus is most commonly found with Culex restuans, Culex pipiens and Aedes atropalpus inartificial containers. In treeholes and tires found deep within woodlands the species may be mixed with small numbers of Anopheles barberi, Orthopodomyia signifera,Orthopodomyia alba & Toxorhynchites rutilus septentrionalis. The closely related treehole species, Aedes hendersoni is known to share habitat with Ae. triseriatus, but little information is available on the range of Ae. hendersoni in New Jersey. Most of the records of Aedes albopictus in New Jersey have come from habitats that contained Ae. triseriatus larvae.
LARVAL COLLECTION: Most of the larval habitat utilized by Aedes triseriatus is too confined to use a standard pint dipper for sampling purposes. As a result, a variety of collecting paraphernalia is needed to sample potential breeding habitat. Many collectors use a large dropping pipette or turkey baster to sample treeholes. Others siphon the entire contents of the treehole into a bucket to save time and maximize the chances of finding rare treehole species. A ladder is useful to sample treeholes at higher elevations. A soup ladle is an effective tool for sampling tires. Aedes triseriatus larvae, however, sound at the slightest disturbance and bury themselves into the leaf litter. Many less common container breeders are missed if dipping the surface is the only method used to sample container habitats. A tea strainer and white pan can be very effective when sampling tires with heavy leaf litter. Passing the strainer back and forth in the tire re-distributes hiding larvae and sifts them out with large amounts of debris. The contents should be transferred to the pan for sorting purposes. It helps to bring a gallon of clear water to clean the pan and flush the samples during the sorting process
Aedes triseriatus larvae are relatively easy to separate from most associate species collected from container habitats. The larvae have a body that is proportionately longer than other species and swim with a characteristic serpentine motion. Larvae have a characteristic grey coloration and the abdominal segments are bulbous giving the larva the appearance of a moving string of beads. Culex species have much longer air tubes and can be accurately sorted from other genera directly in dip samples. Aedes atropalpus is becoming quite common in tires and may well be found with Ae. triseriatus. Their shorter body is useful as a field characteristic and can be confirmed under the microscope by the detached pecten teeth that extend well beyond the midpoint of the siphon. An occasional Orthopodomyia may turn up in samples that are collected from tires but this species is more often found with Ae. triseriatus in treeholes. Aedes albopictus could share habitat with Ae. triseriatus and there are several useful characteristics to isolate Ae. albopictus larvae from field populations of Ae. triseriatus in the laboratory. The air tube of Ae. albopictus has a slightly inflated appearance and is much lighter in color than that of Ae. triseriatus. The anal gills of Ae. albopictus are much longer than the saddle and are equal in size. Aedes triseriatus has much smaller gills and the ventral pair is considerably shorter than the dorsal pair. Aedes triseriatus has a single row of comb scales that are arranged in an extremely irregular fashion. The comb scales of Ae. albopictus are set in a concise single row and are, perhaps, the most diagnostic character for a quick species check in preserved specimens.
Aedes hendersoni also occurs in New Jersey but its distribution is poorly documented and its frequency of occurrence is unknown. The species closely resembles Ae. triseriatus in both the larval and adult stage. Several characters can be used to separate these two species but gill structure is probably the easiest to use in living or freshly preserved specimens. The gills of Ae. triseriatus are tapered and unequal in size. The gills of Ae. hendersoni are considerably larger, equal in size and sausage shaped in structure.
REPRESENTATIVE COLLECTION RECORDS
Northern New Jersey
Location: Newton, Sussex Co.
Date: August 12
Habitat: Spackling Bucket
Instar: 3rd & 4th
Central New Jersey
Location: Keyport, Monmouth Co.
Date : August 14
Habitat : Dish pan
Instar : All instars
Southern New Jersey
Location: Weymouth, Atlantic Co.
Date: May 28
Habitat: Discarded Tires
Instar: 3rd & 4th
IMPORTANCE: Aedes triseriatus has an irritating bite and can be a significant pest. The mosquito can be locally abundant around homes where artificial containers provide plentiful breeding habitat. The mosquito is often cited as a health hazard to eliminate unsightly tire dumps from communities in industrial zoned areas. The mosquito can be a pest of children's playlots where stands of mature trees provide abundant treehole habitat. Aedes triseriatus is a documented vector of LaCrosse encephalitis, a disease that is most common in Midwestern states. The mosquito is an efficient laboratory vector of eastern equine encephalitis but its role as a natural vector has not been documented during outbreaks.