abdomen – the most posterior of the three main body regions, divided into segments called tergites (dorsal half) and sternites (ventral half)

acrostichal – referring to the median longitudinal area of the scutum, from which setae and/or scales often arise

alula – a small lobe along the posterobasal margin of the wing

anal vein – the most posterior wing vein

anepisternum – the region on the side of the thorax composed of the postspiracular area, subspiracular area, and the hypostigmal area located below and behind the spiracle and separated from the katepisternum by the anepisternal cleft

antenna (pl., antennae) – a paired appendage arising from the head and divided into segments including the narrow, ring-like scape, the enlarged pedicel and the distal flagellum which is in turn divided into articles called flagellomeres

antepronotum – a setose lobe located along the anterior margin on the side of the thorax, in front of the postpronotom and above the proepisternum

anterior – part of a structure that is toward, or in the direction of, the front of the mosquito

anterodorsal – referring toward or in the direction of the front and top of the mosquito

apex (pl., apices) – the end or tip of a structure furthest away from the main body

apical – at or referring to the apex of a structure or appendage

apicolateral patches –– the patches of pale scales on the sides of the abdomen that are larger on the apical side of the abdominal segment, usually contiguous with apical transverse bands when present on the tergites

appressed – in reference to scales, meaning lying flat on and possibly touching the body

band – usually refers to a pattern of pale scales such as rings around or transversely across the legs and abdomen

basal – toward, or in the direction of, the base or point of attachment to the main body

basolateral patches – the patches of pale scales on the sides of the abdomen that are larger on the basal side of the abdominal segment, usually contiguous with basal transverse bands when present on the tergites

cercus (pl., cerci) – a small, paired appendage towards the apex of abdomen (in females only) which may or may not be visible, depending on the genus

claw – tiny, paired structure at the apex of each leg, the shape of which can be used as a distinguishing character among species

costa – first of the six major wing veins, located along the anterior margin and extending from the base of the wing to the apex

coxa (pl. coxae)- the most basal segment of the leg, attached to the thorax

cubitus – one of the six major wing veins, located between the media and anal vein, beginning at the base and splitting into two branches, the scaling pattern of which can be used as a distinguishing character among species

desiccated – referring to the drying out of specimens after death, which causes anatomical structures, such as the thorax and abdomen, to fold in on itself, making identification difficult

distal – near or toward the end of an appendage; farther away from the main body

dorsal – the upper surface of any structure as viewed from above

dorsocentral area – the longitudinal area of the scutum located between the submedian and sublateral regions

exserted – visible; protruding from the body

femur – the second segment of the leg located between the coxa and the tibia

flagellomere – an individual unit of the antennal flagellum

flagellum – the third and most distal segment of the antenna, divided into thirteen segments called flagellomeres

fore – towards the front; anterior

fringe – the row of long scales along the posterior margin and the apex of the wing

genitalia – the structures involved in mating located at the end of the abdomen (may or may not be visible)

genus (pl., genera) – a taxonomic classification including one or a group of species having one or a combination of characters

gonocoxite - the largest (and basal) section of the male genitalia

halter (pl., halteres) – a small, paired, club-shaped structure arising from the posterodorsal region of the thorax, just behind and below the wing base (a reduced, modified wing)

head – the most anterior of the three major body regions

hind – towards the back; posterior

hypostigmal area – a small area of the anepisternum located immediately below the spiracle (part of the anepisternum)

inserted – not visible; not protruding from the body

integument – the outer layer of the mosquito body from which scales and setae arise

katepisternum – a large, relatively central section of the thorax located laterally below the anepisternum and above the fore and mid legs

lateral – pertaining to either side of the body; when referring to scutal scaling patterns, located along the margins of the scutum

lateral patches – in reference to abdominal scale pattern, the pale, often triangular-shaped patches of scales located on the sides of the abdomen

lower mesepimeral setae – the setae arising from the mid to lower regions of the mesepimeron, usually one to three and aligned in a row

media – one of the six major wing veins, located between the cubitus and radius, beginning at the base and splitting into two branches

median – in the middle; in reference to scutal scaling patterns, the middorsal area of the scutum from which the acrostichal setae arise

mesepimeron – located laterally on the thorax, the relatively large area behind the katepisternum and above the hind coxa

mesomeron – located laterally on the thorax; a triangular-shaped area between the   mesepimeron and hind coxa

metameron – located laterally on the thorax; a small, narrow area behind the mesepimeron,   mesomeron, and hind coxa

occiput – the posterodorsal part of the head, not distinctly separated from the vertex

palpomere – one individual segment of the maxillary palpus

palpus (pl., palpi) – the paired, segmented appendage (telopodite) of the maxilla arising from the head between the proboscis and the antenna

paratergite – a small, oblong structure along the margin of the scutum between the spiracle   and wing base

pedicel – the enlarged, second segment of the antenna

pleuron – the side of the thorax

pleural – pertaining to the pleuron

plumose – feather-like; as in the long, dense setae of the male antennae

pollinose – having a covering of submicroscopic outgrowths (like pollen)

posterior – pertaining to or near the rear of the mosquito or particular body parts of the mosquito

postprocoxal membrane – the membrane located between the fore coxa and the katepisternum and below the proepisternum (it may be difficult to see if the   specimen is desiccated)

postpronotum – located laterally on the thorax; the round area between the spiracle and   the antepronotum with setae along the posterior margin

postspiracular area – located laterally on the thorax; the raised, rounded area immediately behind and below the spiracle (part of the anepisternum)

postspiracular setae – setae arising from the postspiracular area

prescutellar depression – the round, concave area anterior to the posterior edge of the   scutum, usually without scales or setae

probasisternum – the area on the anterior surface of the thorax, visible above and between   the fore coxa and below the region where the head joins the thorax

proboscis – the long, slender mouthparts arising from the head below the palpi

proepisternum – located on the side of the thorax, below and anterior to the subspiracular area, above and anterior to the katepisternum and the fore coxa

radius – one of the six major wing veins, located between the subcosta and the media; beginning at the base of the wing, it divides three times and terminates in four branches

recumbent - in reference to scales, it means to lie flat on the surface of the integument

scale – a tiny outgrowth from a microscopic socket in the integument, the colour and pattern of which is often used to distinguish among species; may be long and narrow (sometimes even resembling setae) or short and broad, sometimes triangular-shaped

scutal – pertaining to the scutum

scutum – the dorsal surface of the thorax

scutellum – a transverse lobe on the posterior margin of the scutum

seta (pl., setae) – a hair-like growth from the integument, the presence or absence of which is often of taxonomic importance

setose – having setae

species – the basic rank of taxonomic classification; a group of individuals similar in structure and appearance and able to reproduce with each other and bear fertile offspring

spiracle – a small opening into the side of the thorax through which the mosquito breathes; while there are actually more than one, the one located directly behind the postpronotum is of taxonomic importance and for simplicity in this key is referred to as the spiracle

spiracular setae – the setae that arise from the small, triangular-shaped area directly in front of and slightly above the spiracle (not to be confused with the setae arising from the nearby postpronotum)

sternite (pl., sternites) – one of the segments on the ventral side of the abdomen

sternum – the ventral surface of the abdomen

subbasal tooth – a minute structure whose shape and presence or absence as part of the tarsal claw is of taxonomic importance

subcosta – the second of the major wing veins, located between the costa and the radius

sublateral – pertaining to scutal scale patterns, it refers to the longitudinal area between the lateral and submedian areas

submedian – pertaining to scutal scale patterns, it refers to the longitudinal area between the median and sublateral areas

subspiracular area - the area laterally on the thorax below the spiracle and postpronotum and above the katepisternum (part of the anepisternum)

tarsomere – one of the five units of the tarsus (numbered 1 to 5 basal to apical)

tarsus (pl., tarsi) – the distal portion of the leg, divided into five segments called tarsomeres, and connected to the tibia

tergite (pl., tergites) - one of the segments on the dorsal surface of the abdomen

tergum – the dorsal surface of the abdomen

terminalia – the apical abdominal segments that form the genitalia

thorax – the second major body region, between the head and the abdomen, from which the legs and wings arise

tibia – the third segment of the leg, situated between the femur and tarsus

transverse suture – a faint division of the scutum, dividing it into anterior (presutural) and posterior (postsutural) areas

upper calypter – the distal portion of the lobe along the posterior margin of the wing close to the base which may or may not have a fringe of setae, depending on the genus

ventral – pertaining to the under surface of the mosquito or structure

vertex – the region of the head between the eyes and the occiput

wing – the paired, membranous appendage arising from the thorax; the scaling patterns on the veins are taxonomically important

We would like to thank the Ontario Ministry of Health and Long Term Care and Health Canada – First Nations and Inuit Health Branch for inviting us to participate in their West Nile virus mosquito surveillance programs.

For the collection and shipment of specimens to our laboratory for identification purposes, we would like to thank all of the public health units of Ontario and the First Nations and Inuit Health Branch communities that participated in the program. Also, for their mosquito submissions, we would like to thank Canadian Forces Base Borden and Point Pelee National Park.

For the specimens that were unavailable through the West Nile virus program, we are extremely grateful to the Canadian National Collection and the entomologists at Agriculture and Agri-Food Canada in Ottawa, especially Drs. D. M. Wood, Jeff Cumming, J. R. Vockeroth,  and Harold Walther.

We would also like to thank Gregory Ross at the Florida Medical Entomology Laboratory and Trudy  Stanfield for sending mosquitoes that were otherwise unavailable.

We are especially indebted to all of the mosquito identifiers who have worked on the West Nile virus mosquito surveillance project at Brock University, St. Catharines, Ontario including Kelly Baker, Braden Coles, Derek Etherington, Melissa Fox, Claire Garner, Bill Harford, Michelle Hayes, Derek Hogan, Nina Jain, Kirsti Kivinen, Roger Kroeker, Taimi Krys, Sarina Kumar, Alison Leslie, Seetha Liyanage, Rachel MacAlister, Evan Mercier, Anne Ossowski, Conrad Pauls, Emmanuel Popo-Ola, Curtis Russell, Ian Turnbull, Amy Sharp, Matt Skinner, and Lyndsay Smith.

For her illustrations, we would like to acknowledge Kirsti Kivinen.

For their help in Dr. Hunter’s lab (the Fly Lab) at Brock University, we would also like to thank Michael Spironello, Trudy Stanfield, and Matt Patterson.

We would also like to thank Drs. Doug Currie and Chris Darling at the Royal Ontario Museum for the use of the camera that was used to take the photographs found in this key.  And finally, for their review of this work, we would like to thank Drs. Monty Wood, Roy Ellis, Jeffrey Skevington and Robb Bennett.

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