Saskatchewan Aquatic Two-winged Flies (Diptera)

Adult flies have one pair of wings and a pair of little balancing halteres. Beyond this unifying feature there is a great diversity of body types and structures in the adult and larval stages. Larvae usually have elongated bodies, with or without a distinct head and, although they lack true legs prolegs may be present.

The order Diptera is the most diverse order of insects found in aquatic habitats. Over 5100 species in 30 families are reported in North America as having aquatic stages. In Saskatchewan there are aquatic members of at least 16 families. Species lists for families other than the biting flies are in an extremely preliminary state or do not exist due to lack of study in the province.

Diptera have four stages in their life cycle: egg, larva, pupa and adult. The length of each stage is species dependent. The egg stage can last from a few days to a number of weeks. The larval stage consists of four or more instars the duration of which can be from a few days to years. This is followed by pupal and adult stages which last from a couple of days to months. The time required to complete the life cycle varies greatly among the species of the order and depends to a large extent on environmental conditions.

The large number of species in the order is reflected in the variety of microhabitats the larvae live in and the feeding methods exhibited. Fly larvae can be found in all types of aquatic habitats from rivers and streams to lakes, temporary ponds and saline lakes. Some can inhabit grossly polluted habitats such as sewage lagoons and pit toilets (members of the Syrphidae). A number of groups such as the black flies (Simuliidae) live in running water where they attach themselves to rocks or branches and use specially adapted labral fans to filter small particles from the water. Most mosquitoes (Culicidae) also feed by filtering the water column but they are more typical of shallow standing water. Members of the families Syrphidae, Tipulidae and many species of Chironomidae feed on decaying organic matter. A number of families (Chironomidae, Culicidae, Ceratopogonidae and Tabanidae) have predatory species that feed on other insects and invertebrates either by engulfing the prey whole or piercing the skin and sucking out the body fluids. The larvae of the Sciomyzidae or "snail killers" live as parasites on snails and clams.

As adults Diptera feed on a wide variety of foods such as nectar, fungi, decaying vegetation and flesh. However, the public is likely most familiar with the blood feeding of the biting flies (mosquitoes, black flies, no-see-ums, deerflies and horseflies). The females of these groups require a blood meal for egg development.

Gas exchange for most larvae living in running water and many in standing water is through the integument. Many larvae inhabiting standing water breathe through spiracles that they bring in contact with the air at regular intervals. While this restricts the depths at which these larvae can live it also allows them to live in extremely polluted and anoxic conditions. Some members of the Chironomidae, commonly called "blood worms", have developed haemoglobin that is extremely efficient in trapping oxygen. This allows these species to live in the bottom mud of deep lakes where oxygen levels are very low.

Below is a family key to the larvae of commonly collected flies found in aquatic habitats in Saskatchewan. The key has been modified from Clifford (1991).

1a: Larvae with an obvious head.--Go to 2

1b: Larvae appear to be headless.--Go to 14

2a: Parts of labrum developed into fan-like structures ~~~~~ for filtering out particles from water currents. Last two or three body segments enlarged to give the larvae a bottle appearance. End of body has a hold fast structure. First body segment has a proleg.--Simuliidae (Black flies)

2b: Larvae not as above.--3

3a: Two or three pairs of prolegs Arrows indicate prolegs. within first four or five body segments.--4

3b: Larvae not as above.--5

4a:Two pairs of prolegs Arrows indicate prolegs. Body ending in hairs and lobes. Often at water surface.--Dixidae

4b: Three pairs of prolegs Arrows indicate prolegs. present. Body ending in a breathing tube that may be retracted. Body covered by rows of rough tubercles and typically rusty coloured.--Ptychopteridae (False crane flies)

5a: Several body segments with pairs of prolegs Arrows indicate prolegs..--Tipulidae (Crane flies) (In part)

5b: Larval body without prolegs, or with prolegs only on the first body segment, or with prolegs on the first and last body segments.--6

6a: Prolegs present on the first body segment and sometimes on last body segment as well.--7

6b:Prolegs absent or in a few cases small posterior ones.--8

7a: Body setae obvious.--Ceratopogonidae (Biting midges) (In part)

7b: No body setae obvious unless at high magnifications. Anterior and posterior body segments usually with prolegs ~~~~~.--Chironomidae (Non-biting midges, Bloodworms)

8a: First three body segments (thoracic segments) fused and enlarged relative to the other body segments.--9

8b: Body segments not differing significantly in size.--10

9: Single hairs and complex hairs ~~~~~present on body and head. First three body segments fused and enlarged. Often with a breathing structure (siphon) at the posterior end.--Culicidae (Mosquitoes) or to SK Culicidae Database

9b: Two silvery organs~~~~~ visible in anterior and posterior segments. In life body is transparent. Preserved specimens are usually white. Antennae in most developed into a grasping structure.--Chaoboridae (Phantom midges)

10a: Small clawed prolegs present on last body segment.--Ceratopogonidae (Biting midges) (In part)

10b: Prolegs absent.--11

11a: Larvae with extremely thin bodies ~~~~~relative to their length.--Ceratopogonidae (Biting midges) (In part)

11b: Not as above. More robust.--12

12a: Posterior end with short siphon. Body segments divided into two or three subdivisions ~~~~~which often have individual plates on them.--Psychodidae (Moth flies)

12b: Not as above--13

13a: Body relatively hard, leathery~~~~~. Dorsoventrally flattened somewhat. Posterior end often with hairs on it.--Stratiomyidae (Soldier flies)

13b: Body soft and fleshy~~~~~, sometimes covered by fine hairs. Head may be retracted into the body. Posterior end with various lobes surrounding dark breathing holes (spiracles).--Tipulidae (Crane flies)

14a: Body has relatively stiff tubercles and small prolegs~~~~~ on all body segments starting from the third segment.--Athericidae (Snipe flies)

14b: Body structures not as above.--15

15a: End of body has four lobes.~~~~~--Dolichopodidae (Long-legged flies)

15b: Not as above.--16

16a: Body with lobed welts ~~~~~going around the body on most segments. Body tapers toward the front and back ends.--Tabanidae (Horse flies and Deer flies)

16b: Body differs from above.--17

17a: End of body has a long breathing tube(s). --18

17b: Body without long breathing tubes(s).19

18a:One or a split breathing tubeArrows indicate breathing tubes. at the end of body. Usually not as long as body.--Ephydridae (Shore flies)

18b: Breathing tube is usually as long or longer than body~~~~~ when fully extended. Front end of larva blunt. Body sometimes has a fuzzy appearance. Often found in very organically enriched habitats.--Syrphidae (Flower flies)

19a: Body very fleshy~~~~~. Usually extremely wrinkled and distorted when preserved. Blunt body tubercles may be present.--Sciomyzidae (Snail killing flies)

19b: Prolegs present on most abdominal segments. In the most common forms end of body usually with a blunt forked process.--Empididae (Dance flies)

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Mosquitoes (Culicidae)

The female mosquito is the only stage that "bites". Most require a blood meal to produce a full compliment of eggs. They will also feed on nectar, as do the males. People are well acquainted with female mosquitoes but rarely see the males unless they are in mating swarms. The sexes can be easily distinguished. Both have densely scaled bodies, legs and wings. The females have a long proboscis and sparsely haired antennae. The males have a proboscis, bushy antennae, tufted palpi and the end of the abdomen is modified into external genitalia.

The life cycle includes four stages; egg, larva, pupa and adult. Eggs are laid directly into the water or in damp soil in groups or singly. In many species the egg has a "resting stage" known as diapause that prevents the eggs from hatching until the following spring. Other species have more than one generation a year. Some species have desiccation resistant eggs that enable them to withstand consecutive years of drought. Such species can successfully inhabit shallow depressions that contain water for only a short period of time at irregular intervals such as ditches and temporary ponds. The eggs hatch into larvae.

The larvae of most mosquitoes feed on microscopic algae and small organic particles that they filter from the water. They are commonly called "wigglers" which describes their characteristic method of swimming. Larvae pass through 4 growth stages (instars) and then turn into pupae. The pupal stage is a period of major tissue reorganization as the adult body structures develop within it. When the pupal stage ends it swims to the water surface and a split develops along the top of the skin and the adult emerges and flies away.

Identification of adult mosquitoes relies on morphological structures, color patterns of microscopic scales on the abdomen, legs and thorax, coloured hairs on the thorax and claw shapes. The taxonomic keys have been developed using reared specimens that are in pristine condition with a full compliment of scales and hairs. As the adult ages scales and hairs are lost from the body making it very difficult to impossible to accurately identify older specimens.

Over the past few years West Nile Virus has been in the news and of great public concern in SK. The main human vector for the virus in Saskatchewan is Culex tarsalis. An image with diagnostic characters and a brief biology is provided below.

Culex tarsalis DIAGNOSIS: Hind tarsal segments with apical and basal bands of pale scales. Proboscis with a broad median band of pale scales. Third and fourth palpal segments with pale scales. Abdominal segments with a basal band of pale scales. The remainder of each abdominal segment dark scaled. Wings predominantly dark scaled except for a few pale scales at the base of the costa and some on the subcosta. BIOLOGY: Usually larvae are found in permanent and semimpermanent ponds. But they can be found in temporary ponds and even hoof prints in midsummer. The female is the overwintering stage. They survive in caves, burrows or rock piles. Females feed on birds but will also attack mammals this makes them an ideal vector for WNV to humans. There can be as many as four generations per year in the southern parts of the province if conditions are favourable. It can also be a vector of Western equine encephalitis.

Saskatchewan species list of mosquitoes (Culicidae):

(Please note if you do not have a "wheeled" mouse and a list expands below the page bottom just left click on the first entry of the list in question and use the keyboard's down arrow button to scroll down the list.)

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Non-biting Midges (Chironomidae)

The family Chironomidae is one of the most important and diverse groups of aquatic insects found in Saskatchewan. Many have red haemoglobin in their bodies giving them their common name "bloodworms". They are found in almost every freshwater habitat in the province. Some habitats have 80 to 100 species. Chironomids can also occur in large numbers, over 100,000 per square meter if conditions are right. Over 190 species of Chironomidae have been reported from the province even though they have been intensively studied in only a very small number of habitats.

Many dark coloured adult chironomids superficially look like mosquitoes. This has resulted in misidentifications by many people of the swarms of adult chironomids flying over their heads. These swarms are just mating swarms that develop over obvious features such as coloured rocks, signposts, vehicles or people. The "Bug Zapper" developers have used this misidentification to say that the apparatus is killing thousands of mosquitoes when often the majority of bugs being "zapped" are chironomids. Adult chironomids do not bite and most likely do not even feed during their short life time.

Identifying chironomids below the subfamily level is a difficult process compared to other groups of aquatic insects for a number of reasons. There are a large number of genera and species. About 200 have already been recorded from SK and likely there are another 200 or more still to be collected and identified. Most look superficially the same. There are four life stages, larva, pupa, and adult female and male. Most aquatic sampling in SK collects only larvae. The remaining stages are not normally collected, especially the adult stages. Unfortunately, the state of chironomid taxonomy is such that the male is usually needed to identify specimens to species level. Thus, to obtain a species level identification of a larva, pupa or female requires a rearing program be under taken that associates the male with the immature stages. Even to begin the identification process of any of the life stages first requires the specimens to be dissected, cleared (body tissues are chemically digested leaving only cuticle) and then mounted on microscope slides so they can be examined under a high-powered compound microscope.

The dissection procedure to prepare chironomids for mounting on to microscope slides is as follows:

Larvae are best processed whole. If the larva is large small punctures can be made in the cuticle particularly at the "back of the neck" to ensure the chemicals will penetrate into the body tissues. Pupae are separated into the abdomen and cephalothorax. For adults the right legs are removed at the coxae, both wings are pulled off, and the antennae are rolled off. These parts are placed in alcohol until the slide mounting stage. The head, thorax and abdomen are dissected apart and the specimen is ready for the clearing process.

The mounting procedure is also involved. Larvae must be placed so the head is ventral side up and then pressure is applied to the cover slip to spread out the mouthparts for easier viewing (Figure A). Pupae are positioned with the cephalothorax on its side and the abdomen dorsal side up. Pupal exuviae (Figure C) have the cephalthorax and abdomen separated then the cephalthorax is split at the ecdysial line and flipped so the external surface in up and the abdomen is positioned dorsal side up. Adults are arranged in a particular way on the slide using 5 cover slips (Figure B) . The adult thorax is oriented with the left side up, the abdomen with the dorsal side up and the head face up.

Since the specimens are going to be viewed under a compound microscope, which inverts the image, the slide label is placeed upside down on the slide so it can be read easily when the slide is examined.

Saskatchewan species list of Non-biting midges (Chironomidae): Included in the classification are the more widely used subfamily and tribe names.

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Blackflies (Simuliidae)

Blackflies are one of the most persistent pests in the northern and north central parts of the province during the summer months. The immature stages inhabit all types of running water in the area from the large rivers such as the Saskatchewan River to small beaver dam outflows. Under favourable conditions massive numbers of adults can be produced from these habitats resulting in large areas of the province being infested.

Larvae pass through 6 or 7 instars before pupating. They feed on small organic particles that are filtered out of the water column by using highly evolved labral fans. During the summer the larvae take about a month to complete development. The pupal stage takes another five days or so until the adult emerges. After mating the female require a blood meal for egg development. Most species seek out mammals or birds for this meal.

Saskatchewan species list of Blackflies (Simuliidae):

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Biting Midges (Ceratopogonidae)

The adults of many species of ceratopogonids are tiny, hence their common name, "no-see-ums". They can be nuisances if they occur in numbers. Their bite can be irritating and somewhat painful. Fortunately, the adults are usually very localized in their abundance. Not all ceratopogonids feed on mammals; some "bite" other, larger insects such as dragonflies. Others prey upon small flies.

The larvae are generally long, skinny and worm-like, 1 to 1.5 cm long, with a small black head. As larvae, they generally are aquatic or at least semi aquatic. Their diet can range from plant material to small invertebrates depending on species.

Saskatchewan species list of No-see-ums (Ceratopogondiae):

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Horseflies & Deerflies (Tabanidae: Diptera)

These moderate sized flies with their appetite for blood and aggressive behaviour make the tabanids a nuisance for all mammals. One redeeming feature of tabanids is their beautifully patterned eyes and wings. Adults also feed on nectar and honey dew to obtain energy. The blood meal is needed to develop a full compliment of eggs by the female. Eggs are laid on leaves overhanging water. When the egg mass hatches the larvae slide into the water. Larvae live in wet soil or in shallow water. They pass through 5 to 11 instars depending on species. Some are univolitine while others, especially in northern regions require more than one year to complete their life cycle. Little is known about larval feeding although it appears that some are predatory. Pupation occurs in a small chamber above the water level.

Saskatchewan species list of Deer flies & Horse flies (Tabanidae):

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Saskatchewan species lists to misc flies: Please note: Very little detailed systematic work has been done on the misc. aquatic flies that don't bite in SK. For these groups the information is spread throughout the scientific literature and comes from very dated sources. The lists should be viewed only as an extremely preliminary attempt to document the species of the province.

Culicidae References

Darsie, R.F. Jr. and R.A. Ward. 1981. Identification and geographical distribution of the mosquitoes of North America, North of Mexico. American Mos. Control Assoc. Fresno, California.

McAlpine, J.F., B.V. Peterson, G.E. Shewell, H.J. Teskey, J.R. Vockeroth and D.M. Wood. 1981. Manual of Nearctic Diptera. Volume 1, Monograph 27. Can. Gov't. Publ. Centre, Hull, Quebec.

Rempel, J.G. 1953. The mosquitoes of Saskatchewan. Can.J. Zool. 31:433-509.

Rienert, J.F. 2000. New classification for the composite genus Aedes (Diptera:Culicidae:Aedini), elevation of subgenus Ochlerotatus to generic rank, reclassification of the other subgenera, and notes on certain subgenera and species. J. American Mosq. Control. Assoc. 16:175-188.

Stone, A. 1981. Chapter 25: Culicidae. McAlpine, J.F., B.V. Peterson, G.E. Shewell, H.J. Teskey, J.R. Vockeroth and D.M. Wood. Manual of Nearctic Diptera. Volume 1, Monograph 27. Can. Gov't. Publ. Centre, Hull, Quebec.

Wallace, J.R. and Walker, E.D. 2008. Chapter 24: Culicidae. In. Merritt R.W. and K.W. Cummins. Ed. An Introduction to the Aquatic Insects of North America. 4th Edition. Kendall/Hunt Publishing Co. Dubuque, Iowa.

Wood, D.M., P.T. Dang, and R.A. Ellis. 1979. The mosquitoes of Canada. The Insects and Arachnids of Canada. Part 6. Biosystematics Research Institute. Agriculture Canada Ottawa, Ontario.

Chironomide References

Driver, E.A. 1977. Chironomid communities in small prairie ponds: some characteristics and controls. Freshw. Biol. 7:121-134.

Ferrington, L.C. Jr. and W.P. Coffman. 2008. Chapter 26: Chironomidae. In. Merritt R.W. and K.W. Cummins. Ed. An Introduction to the Aquatic Insects of North America. 4th Edition. Kendall/Hunt Publishing Co. Dubuque, Iowa.

Mason, P.G. 1983. Systematics and ecology of Chironomidae (Diptera) associated with Tobin Lake reservoir and the Saskatchewan River. Ph.D. Thesis, Dept. of Biology, University of Saskatchewan, Saskatoon, SK.

Mason, P.G. 1978. A biosystematic study of larval and pupal Chironomini (Diptera: Chironomidae) from the North and South Saskatchewan Rivers. M.Sc.Thesis, Dept. of Biology, University of Saskatchewan, Saskatoon, SK.

Mason, P.G. and D.W. Parker. 1994. Additions and corrections to the list of non-biting midges in Saskatchewan. Blue Jay 52:200-203.

Mason, P.G., D.W. Parker and P. Morrill. 1991. An amateur naturalist's guide to non-biting midges in Saskatchewan. Blue Jay 49:174-182.

Morrill, P.K. 1988. Disturbance of pond Chironomidae communities by deltamethrin insecticide. M.Sc. Thesis, Dept. of Biology, University of Saskatchewan, Saskatoon, SK.

Oliver, D.R., M.E. Dillon and P.S. Cranston. 1990. A Catalogue of Nearctic Chironomidae. Ag.Can. Publ.1857/B.

Parker, D.W. 1992. Emergence phenologies and patterns of aquatic insects inhabiting a prairie pond. Ph.D. Thesis, Dept. of Biology, University of Saskatchewan, Saskatoon, SK.

Parker, D.W. 1985. Biosystematics of Chironomidae inhabiting selected prairie ponds in Saskatchewan. M.Sc.Thesis, Dept. of Biology, University of Saskatchewan, Saskatoon, SK.

Parker, D.W. and N. Glozier. 2005. First record of the non-biting midge, Zavreliella mamorata (Wulp.) (Chironomidae: Diptera), from Saskatchewan. Blue Jay 63: 200-202.

Ceratopogonidae References

Downes, J.A. and W.W. Wirth. 1981. Chapter 28: Ceratopogonidae. In. McAlpine, J.F., B.V. Peterson, G.E. Shewell, H.J. Teskey, J.R. Vockeroth and D.M. Wood. Manual of Nearctic Diptera. Volume 1, Monograph 27. Can. Gov't. Publ. Centre, Hull, Quebec.

Wirth, W. W. 1952. The Genus Alluaudomyia Kieffer in North America (Diptera: Heleidae). Ann. Entomol Soc. Amer. 45:423-434.

Wirth, W.W., A.L Dyce and B.V. Perterson. 1985. An atlas of wing photographs with a summary of the numerical characteristics of the Nearctic speices of Culicoides (Diptera:Ceratopogonidae). Contr. American Ent. Institute 22:1-46.

Simuliidae References

Alder, P.H. and D.C. Currie. 2008 Chapter 25: Simuliidae. In. Merritt R.W. and K.W. Cummins. Ed. An Introduction to the Aquatic Insects of North America. 4th Edition. Kendall/Hunt Publishing Co. Dubuque, Iowa.

Adler, P.H. and P.G. Mason. 1997. Black flies (Diptera: Simuliidae) of east-central Saskatchewan, with description of a new species and implications for pest management. Can. Ent. 129:81-91.

Fredeen, F.J.H. 1985. The black flies (Diptera: Simuliidae) of Saskatchewan. Mus. Nat. Hist. Nat. Hist. Contri. #8.

Fredeen, F.J.H. 1981. Keys to the black flies (Simuliidae) of the Saskatchewan River in Saskatchewan. Quaest. Ent. 17:189-210.

Peterson, B.V. 1981. Chapter 27: Simuliidae. In. McAlpine, J.F., B.V. Peterson, G.E. Shewell, H.J. Teskey, J.R. Vockeroth and D.M. Wood. Manual of Nearctic Diptera. Volume 1, Monograph 27. Can. Gov't. Publ. Centre, Hull, Quebec.

Tabanidae References

Pechuman, L.L. and H.J. Teskey. 1981. Chapter 31: Tabanidae. In. McAlpine, J.F., B.V. Peterson, G.E. Shewell, H.J. Teskey, J.R. Vockeroth and D.M. Wood. Manual of Nearctic Diptera. Volume 1, Monograph 27. Can. Gov't. Publ. Centre, Hull, Quebec.

Teskey, H.J. 1990. The horse flies and deer flies of Canada and Alaska Diptera:Tabanidae. The insects and arachnids of Canada. Part 16. Biosystematics Research Center, Ottawa, Ontario.

Misc References

Byers, G.W. and J.K. Gelhaus. 2008. Chapter 23: Tipulidae. In. Merritt R.W. and K.W. Cummins.Ed. An Introduction to the Aquatic Insects of North America. 4th Edition.Kendall/Hunt Publishing Co. Dubuque, Iowa.

Clifford, H.F. 1991. Aquatic Invertebrates of Alberta. University of Alberta Press.

Courtney, G.W.and R.W. Merritt. 2008. Chapter 22:Aquatic Diptera. Part 1. Larvae of Aquatic Diptera. In. Merritt R.W.and K.W.Cummins. Ed. An Introduction to the Aquatic Insects of North America. 4th Edition. Kendall/Hunt Publishing Co. Dubuque, Iowa.

McAlpine, J.F., B.V. Peterson, G.E. Shewell, H.J. Teskey, J.R. Vockeroth and D.M. Wood. 1981. Manual of Nearctic Diptera. Volume 1, Monograph 27. Can. Gov't. Publ. Centre, Hull, Quebec.

McAlpine, J.F., B.V. Peterson, G.E. Shewell, H.J. Teskey, J.R. Vockeroth and D.M. Wood. 1987. Manual of Nearctic Diptera. Volume 2, Monograph 28. Can. Gov't. Publ. Centre, Hull, Quebec

McFadden, M.W. 1972. The soldier flies of Canada and Alaska (Diptera:Stratiomyiidae) I Beridinae, Saginae, and Clitellarinae. Can. Ent. 104:531-562.

McFadden, M.W.1967. Soldier fly larvae in America north of Mexico. Proc. Nat. Mus. Smith. Inst. 12:1-72

Merritt, R.W. and D.W. Webb. 2008. Chapter 22: Aquatic Diptera. Part 2. Pupae and Adults of Aquatic Diptera. In. Merritt R.W. and K.W. Cummins. Ed. An Introduction to the Aquatic Insects of North America. 4th Edition. Kendall/Hunt Publishing Co. Dubuque, Iowa.

Peters, T.M. and E.F. Cook. 1966. The Nearctic Dixidae (Diptera). Minn. Agric. Exp. Stat. #55101 233-278

Quate, L.W. 1959. Classification of the Psychodini Psychodidae: Diptera. 52:444-451

Stone et al 1965. A catalog of the Diptera of America North of Mexico. U.S. Dept. of Agric. Agr. Hdbk #276 1696 pp.

Saskatchewan Aquatic Two-winged Flies (Diptera)

Mosquitoes (Culicidae)

Non-biting Midges (Chironomidae)

Blackflies (Simuliidae)

Biting Midges (Ceratopogonidae)

Horseflies & Deerflies (Tabanidae: Diptera)

GENERAL AQUATIC "BUG" INFO

SK AQUATIC INSECTS ORDERS

AQUATIC NON-INSECTS