Saskatchewan Aquatic Beetles (Coleoptera)
The beetles as adults are easily identified by the elytra or harden shell-like forewings. The size can range from 2 mm to 3 cm depending on family and species. The larvae are much more variable in form. Some have large fang-like mandibles while others have chewing mouthparts. The legs can be reduced or well developed. The abdomen can have lateral projections on it or dorsal ornamentation. Size can vary as much as the size as the adult.
The largest order of insects is the Coleoptera with over 250,000 species. Only about 5000 species have aquatic stages. Even so the beetles are one of the most diverse freshwater macroinvertebrate groups. Eighteen families have species with at least one aquatic life stage. Only nine aquatic families occur in Saskatchewan. So far over 230 species of aquatic beetles have been reported or are likely to occur in Saskatchewan. About half belong to the family Dytiscidae.
The life cycle has four stages; egg, larva, pupa and adult. The number of stages that are aquatic varies among and within groups. However, with rare exceptions, the pupal stage is terrestrial.
Coleoptera are found in all types of aquatic habitats but the diversity is highest in lentic (standing) water. Evolutionary evidence suggests they invaded aquatic systems on many occasions. Each invasion resulted in different adaptations. This makes generalizations regarding ecology and life histories difficult. The Hydrophilidae have predatory larvae and the adults are omnivorous or herbivorous. Most Dytiscidae are predaceous in both stages. Predatory beetles either engulf their prey or grasp the prey with fang-like mandibles and inject digestive enzymes into the prey's body. The resulting "soup" is sucked out. Beetle larvae usually "breathe" through their integument (skin) or gills. Others use terminal spiracles that are protruded above the water surface. Adults carry an air bubble under the elytra or in hydrofuge body hairs that they must periodically return to the water surface to replenish.
Special mention should be made of the Dytiscidae. This family is the most diverse, largest (Dytiscus) and abundant aquatic beetle family in Saskatchewan. They inhabit all types of water bodies but due to their reliance on atmospheric oxygen are restricted to the shallow margins. Apparently, all species in the Saskatchewan have only one generation per year. Eggs are laid in spring by over wintering females and hatch soon after laying. The larval stage has three instars. Prior to pupation the final instar larvae crawl out of the water and dig a pupal chamber in litter along the shore. After a short pupation the adult emerges. Some of the larger species are able to live for more than one year in ideal conditions.
The dytiscids usually go unnoticed by the general public except in the fall and during the spring. In the spring many species disperse, as adults, from their overwintering habitats in rivers, lakes and larger ponds to the more temporary and smaller ponds that dot the landscape. These smaller habitats provide more food resources ie mosquito larvae and other insects and more heat units for faster growth. Breeding occurs and the larvae develop to maturity. By August the new generation of adults begin a migration back to their overwintering habitats. During this time there may be large numbers of beetles seen flying around, into and under lights and shiny surfaces. Unfortunately, vast quantities of these adults die due to this light attraction.
Another family of note is the Gyrinidae. This family is one of the most conspicuous and curious beetles found in Saskatchewan waters. Adults are usually seen in groups at the water surface swimming in a rapid and erratic manner. This behaviour gives them their common name of "whirligig beetle". The adult eyes are divided into upper and lower portions. This marvellous adaptation allows the beetles to live at the water surface and be able to see above and below without any distortion caused by the air/water interface.
Below is a family key to the larvae and adults of common aquatic beetles found in Saskatchewan. An interactive pdf version of the key is available by emailing me and requesting a copy. Please note that some uncommon larvae and adults are not keyed.
1a: Wings absent. Larvae.--2
1b: Elytra (hard fore wings) present. Adult beetles. Found in water or at times flying around lights.--Go to 10
2a: Legs made up of five segments.--3
2b: Larvae with only four segmented legs.--5
4a: Two claws at the end of each leg. Gill filaments present on abdominal segments. Four hooks at the end of the abdomen.--Gyrinidae (SK Gyrinidae Distribution Maps) (Note Berosus (Hydrophilidae) has lateral filaments but lacks four claws at the end of the abdomen and has four leg segments.)
5a: Antennae very long, much longer than head.--Scirtidae (Marsh Beetles)
5b: Antennae at most just slightly longer than head, usually much shorter.--6
6b: Abdomen with nine or ten abdominal segments. Abdomen usually with extensive hard plates.--8
7a: Head obvious and well developed. Mandibles distinct. Legs usually well developed.--Some Hydrophilidae (Water Scavenging Beetles) (SK Hydrophilidae Distribution Maps)
7b: Head greatly reduced. Mouthparts not obvious. Legs greatly reduced. Maggot like.--Chrysomelidae (Leaf Beetles)
8a: Abdomen with nine segments.--9
8b: Abdomen with ten segments. The tenth segment is between two ceri.--Hydraenidae (Minute Moss Beetles)
9b: No operculum on segment 9.~~~Some Hydrophilidae (Water Scavenging Beetles) (SK Hydrophilidae Distribution Maps)
10b: Eyes normal, not divided in two.--11
11b: No plates on ventral surface covering legs or abdominal segments.--12
Saskatchewan species list of aquatic beetles (Coleoptera):
Haliplidae (Water crawling beetles)
- Brychius hornii Crotch 1873 ??
- Haliplus apicalis Thomsen
- Haliplus borealis LeConte
- Haliplus canadensis Wallis
- Haliplus cribrarius LeConte
- Haliplus immaculicollis Harris
- Haliplus stagninus Leech
- Peltodytes edentulus LeConte
- Peltodytes tortulosus Roberts
Gyrinidae (Whirligig beetles)
- Dineutes assimilis (Kirby)
- Dineutes horni Roberts
- Gyrinus affinis Aube'
- Gyrinus aeneolus LeConte
- Gyrinus aeratus Stephens
- Gyrinus aquiris LeConte
- Gyrinus bifarius Fall
- Gyrinus cavatus Atton
- Gyrinus confinis LeConte
- Gyrinus consobrinus LeConte
- Gyrinus dichrous LeConte
- Gyrinus dubius Wallis
- Gyrinus fraternus Couper
- Gyrinus hoppingi Leech
- Gyrinus latilimbus Fall
- Gyrinus maculiventris LeConte
- Gyrinus minutus Fabricius
- Gyrinus opacus Sahlberg
- Gyrinus pectoralis LeConte
- Gyrinus picipes Aube'
- Gyrinus pleuralis Fall
- Gyrinus puginois Fall
- Gyrinus punctellus Ochs
- Gyrinus sayi Aube'
- Gyrinus ventralis Kirby
- Gyrinus wallisi Fall
Chrysomelidae (Flower beetles)
- Donacia canadensis Askevold
- Donacia distincta LeConte
- Donacia fulgens LeConte
- Donacia hirticollis Kirby
- Donacia magnifica LeConte
- Donacia porosicollis Lacordaire
- Donacia proxima Kirby
- Donacia pubescens LeConte
- Donacia subtilis Kunze
- Plateumaris chalcea (Lacordaire)
- Plateumaris flavipes (Kirby)
- Plateumaris frosti (Schaeffer)
- Plateumaris fulvipes (Lacordaire)
- Plateumaris germari (Mannerheim)
- Plateumaris pusilla (Say)
- Plateumaris robusta (Schaeffer)
Elmidae (Riffle Beetles)
- Dubiraphia vittata (Melsheimer)
- Optioservus divergens (LeConte)
- Optioservus fastiditus (LeConte)
- Stenelmis vittipennis Zimmerman
- Limnebius sp
- Ochthebius cribricollis LeConte?
- Ochthebius kaszabi Janssens
- Ochthebius lineatus LeConte
- Ochthebius marinus (Paykull)
- Cyphon pusillus (Leconte)
- Cyphon variabilis (Thunberg)
- Microcara explanata LeConte
Hydrophilidae (Water scavenging beetles)
- Anacaena limbata (Fabricius)
- Berosus fraternus LeConte
- Berosus hatchi Miller
- Berosus oregonensis Miller
- Berosus striatus (Say)
- Crenitis digesta (LeConte)
- Crenitis morata (Horn)?
- Cymbiodyta acuminata Fall
- Cymbiodyta vindicata Fall
- Cymbiodyta minima Notman
- Enochrus diffusus (LeConte)
- Enochrus hamiltoni (Horn)
- Enochrus ochraceus (Melsheimer)?
- Enochrus cinctus (Say)
- Helophorus columbianus McCorkle
- Helophorus eclectus d'Orchymont
- Helophorus frater Smetana
- Helophorus furius Smetana
- Helophorus inflectus McCorkle?
- Helophorus lacustris LeConte
- Helophorus leechi McCorkle
- Helophorus linearis LeConte?
- Helophorus linearoides d'Orchymont
- Helophorus nitiduloides d'Orchymont
- Helophorus nitidulus LeConte
- Helophorus oblongus LeConte
- Helophorus orientalis Motschulsky
- Helophorus sempervarians Angus
- Helophorus tuberculatus Gyllenhal
- Hydrobius fuscipes (Linnaeus)
- Hydrochara obtusata (Say)
- Hydrochus currani Brown?
- Hydrochus granulatus Blatchley?
- Hydrochus pseudosquamifer Miller?
- Hydrochus squamifer LeConte
- Hydrophilus triangularis Say
- Laccobius agilis (Randall)?
- Laccobius borealis Cheary?
- Laccobius carri d'Orchymont
- Laccobius cinereus columbianus Miller
- Laccobius columbianus Miller
- Laccobius reflesipenis Cheary?
- Laccobius spangleri Malcolm
- Laccobius truncatipenis Miller
- Paracymus despectus (LeConte)
- Paracymus subcupreus (Say)?
- Tropisternus lateralis numbatus (Say)
Dytiscidae (Diving beetles)
- Laccophilus biguttatus Kirby
- Laccophilus maculosus decipiens Say
- Laccornis conoideus (LeConte)
- Desmopachria convexa (Aube')
- Liodessus cantralli (Young)
- Liodessus fuscatus (Crotch)
- Liodessus obscurrellus (LeConte)
- Hygrotus compar (Fall)
- Hygrotus farctus (LeConte)
- Hygrotus impressopunctatus (Schaller)
- Hygrotus infuscatus (Sharp)
- Hygrotus laccophilinus (LeConte)
- Hygrotus marklini (Gyllenhal)
- Hygrotus masculinus Crotch
- Hygrotus patruelis (LeConte)
- Hygrotus picatus (Kirby)
- Hygrotus punctilineatus (Fall)
- Hygrotus salinarius (Wallis)
- Hygrotus sayi J. Balfour-Browne
- Hygrotus sellatus (LeConte)
- Hygrotus suturalis (LeConte)
- Hygrotus tumidiventris (Fall)
- Hygrotus turbidus (LeConte)
- Hygrotus unguicularis (Crotch)
- Sanfilippodytes brumalis (Brown)
- Sanfilippodytes pseudovilis (Young)
- Neoporus dimidiatus (Gemminger and Harold)
- Neoporus superioris (Balfour-Browne)
- Neoporus undulatus (Say)
- Neoporus vittatus (LeConte)
- Hydroporus appalachius Sherman
- Hydroporus badiellus Fall
- Hydroporus columbianus Fall
- Hydroporus dentallus Fall
- Hydroporus fuscipennis Schaum
- Hydroporus larsoni Nilsson
- Hydroporus morio Aube'
- Hydroporus nigellus Mannerheim
- Hydroporus notabilis LeConte
- Hydroporus obscurus Stram
- Hydroporus occidentalis Sharp
- Hydroporus pervicinus Fall
- Hydroporus puberulus LeConte
- Hydroporus rectus Fall
- Hydroporus rufinasus Mannerheim
- Hydroporus signatus Mannerheim
- Hydroporus striola (Gyllenhal)
- Hydroporus tenebrosus LeConte
- Hydroporus tristis (Paykull)
- Hydrocolus paugus (Fall)
- Hydrocolus rubyae (Larson)
- Hydrocolus stagnalis (Gemminger and Harold)
- Stictotarsus griseostriatus (DeGeer)
- Stictotarsus spenceri (Leech)
- Stictotarsus striatellus (LeConte)
- Nebrioporus depressus (Fabricius)
- Nebrioporus macronychus (Shirt)
- Oreodytes laevis (Kirby)
- Oreodytes scitulus (LeConte)
- Agabus ajax Fall
- Agabus ambiguus (Say)
- Agabus antennatus Leech
- Agabus anthracinus Mannerheim
- Agabus approximatus Fall
- Agabus arcticus (Paykull)
- Agabus audeni Wallis
- Agabus austinii Sharp
- Agabus bicolor (Kirby)
- Agabus bifarius (Kirby)
- Agabus canadensis Fall
- Agabus confinis (Gyllenhal)
- Agabus discolor (Kirby)
- Agabus elongatus (Gyllenhal)
- Agabus erichsoni Gemminger & Harold
- Agabus falli (Zimmermann)
- Agabus fuscipennis (Paykull)
- Agabus griseipennis LeConte
- Agabus inscriptus (Crotch)
- Agabus leptapsis (LeConte)
- Agabus margaretee larson
- Agabus obliteratus nectris Leech
- Agabus opacus Aube'
- Agabus phaeopterus (Kirby)
- Agabus punctulatus Aube'
- Agabus semipunctatus (Kirby)
- Agabus seriatus (Say)
- Agabus strigulosus (Crotch)
- Agabus thomsoni (Sahlberg)
- Agabus tristis Aube'
- Agabus triton Fall
- Agabus wasastjernae (Sahlberg)
- Carrhydrus crassipes Fall
- Ilybius angustior (Gyllenhal)
- Ilybius discedens Sharp
- Ilybius fraterculus LeConte
- Ilybius picipes Kirby
- Ilybius pleuriticus LeConte
- Ilybius subaenus Erichson
- Coptotomus longulus LeConte
- Neoscutopterus angustus (LeConte)
- Neoscutopterus hornii (Crotch)
- Rhantus binotatus (Harris)
- Rhantus consimilis Motschoulsky
- Rhantus sericans Sharp
- Rhantus sinuatus (LeConte)
- Rhantus suturellus (Harris)
- Rhantus wallisi Hatch
- Colymbetes dahuricaus Aube'
- Colymebetes densus LeConte
- Colymbetes exaratus LeConte
- Colymbetes paykulli Erichson
- Colymbetes sculptilis Harris
- Dytiscus alaskanus J. Balfour-Browne
- Dytiscus circumcinctus Ahrens
- Dytiscus cordieri Aube'
- Dytiscus dauricus Gebler
- Dytiscus fasciventris Say
- Dytiscus harrisii Kirby
- Dytiscus hybridus Aube'
- Dytiscus marginicollis LeConte
- Dytiscus verticalis Say
- Hydaticus aruspex Clark
- Hydaticus piceus LeConte
- Acilius athabascae Larson
- Acilius semisulcatus Aube'
- Acilius sylvanus Hilsenhoff
- Graphoderus liberus (Say)
- Graphoderus occidentalis Horn
- Graphoderus perplexus Sharp
Bousquet, Y.(ed) 1991. Checklist of Beetles of Canada and Alaska. Agriculture Canada.
Hooper, R. 2003. Pers. Comm.
Larson, D.J. 1987. Aquatic Coleoptera of peatlands and marshes in Canada. Mem. Ent. Soc. Can. 140:99-132
Larson, D.J., Y. Alarie and R.E. Roughley. 2000. Predaceous diving beetles (Coleoptera: Dytiscidae) of the Nearctic Region, with emphasis on the fauna of Canada and Alaska. NRC Res. Press, Ottawa, ON.
Mousseau, T. and R.E. Roughley. 2007. Taxonomy, classification, reconstructed phylogeny and biogeography of Nearctic species of Brychius Thomson (Coleoptera: Haliplidae). The Coleopterist's Bull. 61:351-397.
Smetana, A. 1988. Review of the family Hydrophilidae of Canada and Alaska (Coleoptera). Mem. Ent. Soc. Can. 142:1-316.
White, D.S. and R.E. Roughley. 2008. Chapter 20. Coleoptera. In. Merritt R.W., K.W. Cummins and M.B. Berg. Ed. An Introduction to the Aquatic Insects of North America. 4th Edition. Kendall/Hunt Publishing Co. Dubuque, Iowa.