Photographic Key to the Adult Female Mosquitoes (Diptera: Culicidae) of Canada
Aynsley C. Thielman
,
Fiona F. Hunter
Brock University, Department of Biological Sciences, St. Catharines, Ontario, L2S 3A1, Canada. athielman@brocku.ca, hunterf@brocku.ca
Photographic Key to the Adult Female Mosquitoes (Diptera: Culicidae) of Canada
Photographic Key to the Adult Female Mosquitoes (Diptera: Culicidae) of Canada
Aynsley C. Thielman
,
Fiona F. Hunter
Brock University, Department of Biological Sciences, St. Catharines, Ontario, L2S 3A1, Canada. athielman@brocku.ca, hunterf@brocku.ca
Abstract
There are currently 82 species of mosquitoes (Diptera: Culicidae) in 10 genera known from Canada. Dichotomous keys to the adult females are provided in two formats (HTML and PDF). Photographs of diagnostic characters accompany the text descriptions in each couplet for ease in identification. Included are: an introduction to mosquito identification, instructions for using this particular key, anatomical diagrams, and a glossary of terms. Descriptions of recently introduced and potential species are also provided.
Aedes japonicus (Culicidae) Photo by S. A. Marshall
Introduction
Mosquitoes are common insects throughout most of the world. Their requirement for a blood meal for egg development makes them potential vectors of disease. Whether for research or control measures, the correct identification of adult female mosquitoes to species is essential. For information on collection methods, general biology, and geographic distribution, refer to Wood et al. (1979). There are many keys available to identify mosquitoes and this particular key is meant as a supplement to other publications. This key contains digital photographs of taxonomically important characters to make correct identifications easier.
In order to use any key, it is necessary to have a good understanding of anatomical terms. For less experienced identifiers, there are illustrations and a glossary included in this key which should be thoroughly studied before attempting mosquito identification. Very simply, the body is divided into three segments: head, thorax, and abdomen. The thorax supports one pair wings and three pairs of legs. It is mainly the presence or absence of setae (long, hair-like structures) and the position and colour of scales (smaller, flatter structures) on the head, thorax, wings, legs, and abdomen that are used to identify adult female mosquitoes. More detailed descriptions of structures are found in the anatomy section of this key as well as in other keys and entomological publications. Keep in mind that different authors may use different terms for the same anatomical structures.
Identification keys generally use the most common characteristic among a specific group of specimens examined. Therefore, when a large number of mosquitoes are identified, there will likely be some variation within species (e.g. differences in size, colour, morphology, etc.). Possible reasons include temperature differences, environmental conditions, or geographical location, to name just a few. If unsure of one’s identification, it is a good idea to double check identifications with other keys and/or more detailed descriptions of that particular species, especially if it is a rare or possibly newly introduced species. Regardless of experience, when identifying mosquitoes, it is best to always start at the very beginning of the key, at the genus level, and follow each step until a correct identification is reached. Assumptions based on general appearances often lead to identification errors.
Finally, we recommend that you maintain a reference collection of identified, pinned specimens for double-checking identifications.
How to Use This Key
This key works in the same fashion as other dichotomous identification keys. The objective is to choose characteristics that best represent the mosquito in question. There is usually more than one characteristic described in each couplet, with the first one mentioned being the most important feature to consider. However, due to their extremely fragile nature, specimens are rarely in excellent condition, especially when caught in light or gravid traps which use a fan to capture specimens. For more experienced identifiers, the decision may then sometimes be based on other characteristics. If unsure, it is preferable to refer to the mosquito as an unknown or unidentifiable species.
Each step in the key will have one or two photographs to help you decide which characters most closely resemble the specimen in question. Factors such as the age of the specimen and the type of photographic equipment used when taking the pictures contained in this key have influenced the degree of likeness to freshly trapped specimens. In particular, some of the pictures cause the specimens to appear more red than they actually are. Therefore, it is important to read the captions that accompany the photographs as well as studying the images, particularly with reference to scale colour. Choose the option that best describes the mosquito in question and end at the correct identification which is written in red. Please note that the species names within the image refer to the specimen in the picture and are not necessarily the correct identification. Always begin at the genus level and continue until you reach a species name in red or can’t go any further due to the condition (e.g. missing characters) of the specimen.
Throughout the key there will be Notes to help you in your identifications. There is an Appendix which includes more detailed descriptions of some species, a Glossary of terms, and a section on Recently Introduced Mosquitoes to Canada. Something to note when identifying mosquitoes: sometimes loose scales can adhere to the mosquito, leading to incorrect identifications - be sure scales originating from the anatomical region being examined are not displaced from elsewhere.
Mosquito Anatomy
Species Key
Glossary
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
Acknowledgements
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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Cite
Thielman, A.C, and Hunter, F.F. 2007. Photographic Key to the Adult Female Mosquitoes (Diptera: Culicidae) of Canada. Canadian Journal of Arthropod Identification No. 4, 14 December 2007, available online at doi: 10.3752/cjai.2007.04.
