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Identification and Life Histories of Common Aquatic Insects

 

By Kenneth Williams

Aquatic insects are an important but often overlooked part of pond life. Ecologically, the insects perform a variety of functions dependent on species. Some are detritus feeders that break down dead plant and animal tissue and return it to the environment as excretory products or as a food item for other aquatic animals. Many aquatic insects are predatory in at least one of their life cycle stages. Some are highly voracious and feed on fish, tadpoles and other larger creatures.

Insects form a large part of the diet of most fish species. For this reason a healthy insect population is of considerable interest to the sportsman or pond owner interested in a productive pond fish population. Fly fishermen have long known the importance of insects in the diet of fish and have developed lures that match predominant insect species such as mayflies.

Aquatic insects, like their terrestrial counterparts, go through several developmental stages known as instars. In some species the final immature instar forms a pupa that develops into the mature adult form. Each instar stage in most species is followed by a molt into a more developed form.  However, some species have quite distinct larval stages.

 Respiration is a major concern for air breathing organisms in an aquatic environment. Aquatic insects have adapted to breathing under water in several ways depending on species. Many species draw air into spiracles (breathing openings on the abdomen) through tubes that pierce the water surface.  Others are equipped with a dense pad of fine, short hair on the thorax or abdomen that traps enough air for long periods of submerged activity. The air bubble must be replenished by returning to the water surface or in some species by coming into contact with oxygen bubbles on the leaves of submerged aquatic plants.  The air bubble formed by hair pads or other mechanisms often forms a silvery bubble or sheen on the ventral side of the insect or at the tip of its abdomen. Most nymphal stages are provided with gills or gill-like structures to provide oxygen to the organism.

 An understanding and familiarity with the aquatic insects will increase appreciation for the diversity of life to be found in the pond and knowledge of an important ecological component of the aquatic environment. Healthy natural fish populations require an abundant insect community.

Ephemeroptera – mayflies

            Family – Ephemeridae – common burrowers

                 Hexegenia spp.

Hexagenia adult mayfly                       

Hexigenia larvae

 

 

 

 

 

 

 

 Description: Adults are soft bodied; and have 2 pairs of veined, membranous, triangular shaped wings. Fore wings are much larger than hind wings. Wings are held above the body. Two, or more usually three long tails (cerci) are present extending from an elongate abdomen. Eyes are well developed and the fore legs are long and held together in a forward arc when at rest. Mouth parts are non-functional. There are about 13 species in North America.

 Mayfly nymphs are elongate forms 3-32 mm, with plume-like gills attached to abdominal segments.  They have well developed legs, usually with a single claw; and 2-3 tails. Wing pads are present. Tusks are present and tips curve upward and outward in burrowing species.

 Habitat: Most species of mayfly inhabit stream habitats, however, many species are commonly associated with ponds and lakes. Pond species nymphs are often burrowers in the pond substrate. Some species leave burrows at night and forage for food.

 Food habits: Adults do not feed. Nymphs are usually detritivores or herbivores consuming microscopic algae, and bits of organic matter. Burrowing particle feeders may ingest some sediment as they feed. 

Life History: Nymphs require a year or more to develop into adults, although it can take anywhere from a few weeks to 2 years.  When ready to transform into the winged sub-imago stage, they float to the surface and molt. The sub-imago (also called a “dun”) flies to shore and rests on vegetation until the final molt, usually the following day, into an adult. Molts are often synchronized and called a “hatch”; or transformation may be spread over several weeks. Synchronization may be caused by temperature, photoperiod or a combination of both and other environmental factors. Mayfly hatches can result in large swarms covering the sides of buildings, roads and other nearby objects.  Swarms are composed mainly of male insects. As females enter the swarm, males seize them and fly off to mate. Females deposit eggs on the water surface or the eggs may be attached to vegetation, sticks or other objects emerging from the water.

 Mayflies are a significant diet item for many other fish and insect species. They also are used as biological indicators of water quality as many species are susceptible to water pollution or only occur in specific environments.

 Odonata –dragonflies and damselflies

            Anisoptera - dragonflies

                        Aeshnidae

                                    Anax junius - Green darner

Anax junius - Green darner nymph

 

 

 

 

 

 

 

 

Description: Adults are up to 76 mm long with a green thorax and bluish abdomen. Wings consist of 2 pair with hind wings slightly larger at base than front wings. Wings are held horizontally when at rest. A spot within a circle mark is present on the upper part of the face. Compound eyes are in contact dorsally along much of the edge.

 Nymphs are 31-50 mm with an elongated, tapering abdomen terminating in triangular ceri. The larvae breathe by gills located in the abdomen. Water is drawn in through the anus and circulated over the gills. Water can be rapidly expelled through the anus to provide a “jet propelled” form of locomotion. Legs are slender.

 It can be difficult to distinguish species of Odonata nymphs. Their coloration varies with diet and environment. Also, body structure changes somewhat with each molt.

 Habitat: Adults are found around ponds and quiet, shallow areas of lakes. Most larvae are sprawlers on the pond bottom or climb among vegetation and other material. Some burrow.

 Food habits: Most dragonflies feed on flying insects caught in the basket-like arrangement of their legs. Prey consists of mosquitoes, midges, flies, moths and other flying insects. Dragonflies are also known as “mosquito hawks” or “hawkers” because of their predatory behavior.

 Larvae are voracious predators attracted visually by motion. They hide themselves in vegetation or burrows and await prey. Nymphs feed on small aquatic organisms including small fish and tadpoles. Nymphs can be cannibalistic. Prey is captured with an extendable labium which is folded under the head when not in use. The labium is extended to capture prey with claw-like lateral appendages. The labium is usually at least 1/3 of total body length. Dragonfly larvae can cause significant mortality in channel catfish fingerling production ponds and are routinely eradicated from these facilities.

 Life history: Males are more brightly colored than females. Males of many species establish territories. Many species have characteristic flight behaviors.  Unlike other insects, male copulatory organs are on the second body segment. The male must flex the abdomen down and forward to transfer sperm from the genital opening on the abdomen tip to this second segment. Male and females spend much time flying “in tandem”.  The male clasps the female behind the back of the head with pincer-like appendages at the tip of the abdomen. Copulation occurs in flight. The female bends the tip of her abdomen forward and contacts male genitalia in the second abdominal segment to collect sperm.

 The female then may lay eggs while the male guards her to prevent other males from grabbing and flying off in tandem with her. Eggs are laid on the water surface with a tapping motion as the insect flies over.

 Usually one generation is produced annually with over-wintering larvae. Larval development depends on temperature and food supply.  Fully developed nymphs crawl out of the water onto plant stems or other objects for the final molt. A few days are needed for the insect to reach its full flight potential and 1-2 weeks are required for full color development. Adults emerge spring through fall. Occasionally mass flights of dragonflies occur over long distances for no known reason. Some species of Anax are migratory.

 

 Dragonflies may be found that are dotted with red colored, pin head sized, larval water mites. The mites are usually attached to the thorax and abdomen. They feed on the dragonfly 2-3 weeks apparently causing no harm, before returning to the water to develop into adult water mites.

 Dragonfly larvae are important food items in the pond for many fish species and frogs.

 

 

 

 

 

Anisoptera - dragonflies

            Libellulidae – common skimmers

                                    Libellula lydia - common whitetail skimmer

 

 

 

 

 

 

 

 

 

Description: Adults are up to 76 mm in length.  Wings are marked with bands or spots, with a wing spread of about 64 mm.  There is a broad dark band in the center of each wing. The dorsal side of the abdomen is powdery blue to nearly white. Skimmer adults have erratic flight patterns.

 Larvae have hairs on legs and abdomen. The abdomen is somewhat shorter and flattened than darner dragonfly larvae, and it may have lateral spines.

 Habitat: Common skimmer larvae are sprawlers on the pond substrate or found climbing through vegetation. They inhabit the littoral zone and can tolerant low dissolved oxygen levels. Adults are found over and near ponds.

 Food habits: Larval and food habits similar to the green darner. The larvae are predaceous and feed on small aquatic organisms including small fish. Adults eat mosquitoes, flies moths and other flying insects.

 Life history: Males are more brightly colored than females. Male copulatory organs are on the second body segment. The male must flex the abdomen down and forward to transfer sperm from the genital opening on the abdomen tip to this second segment. Male and females spend much time flying “in tandem”.  The male clasps the female behind the back of the head with pincer-like appendages at the tip of the abdomen. Copulation occurs in flight. The female bends the tip of her abdomen forward and contacts male genitalia in the second abdominal segment to collect sperm.

 Eggs are laid on the surface of the water. Female flies low over the water, dipping her tail and washing eggs off the tip. 

Odonata –dragonflies and damselflies

            Zygoptera - damselflies

                        Coenagrionidae – narrow-winged damselflies

                                    Enallagma basidens - double-striped bluet

Description: In adults the wings are narrowly constricted at the base. The body is colored light blue with black markings. Wings are held together over the body when at rest. Males are usually more brightly colored than females.   The larvae are 13-25mm in length and stout bodied. There are 3, broad and leaf-like caudal lamellae, that are pointed at the tips. Antennae segments about the same length.  The labium does not have long stalk-like base.

Habitat: Adults are found among the marginal vegetation of ponds and slow streams. Larvae are sprawlers on the pond substrate or found crawling through vegetation.

Food habits: Adults eat soft bodied insects such as aphids. Larvae feed on other aquatic insects.

Life history: Maximum adult damselfly life is about 3-4 weeks. Male copulatory organs are on the second body segment. The male must flex the abdomen down and forward to transfer sperm from the genital opening on the abdomen tip to this second segment. Male and females spend much time flying “in tandem”.  The male clasps the female behind the back of the head with pincer-like appendages at the tip of the abdomen. Copulation occurs in flight. The female bends the tip of her abdomen forward and contacts male genitalia in the second abdominal segment to collect sperm.

Females have ovipositor and insert eggs into plant tissue. Sometimes as much as 12 inches below water surface.  Eggs hatch in 1-3 weeks.

Order Hemiptera – True bugs

            Suborder - Hydrocorizae

            Corixidae – water boatmen

                                    Water boatman - Sigara alternate

Description: Adults 3-11 mm in length. They are somewhat flattened oval –shaped bugs with parallel sides. The dorsal surface is finely lined and the body is yellow to gray in color. The beak is triangular with distinct transverse grooves. Fore legs are short with a modified scoop-shaped tarsus. Hind legs are oar-like with swimming hairs. The water boatman is sometimes confused with the back swimmer. Water boatmen are rapid, erratic swimmers. They carry an air bubble below the water surface for breathing and are capable of making a chirping sound by stridulating the base of the fore femora against the sharp lateral edge of the head.

Habitat: Found in running and quiet waters

Food habits: Water boatmen feed on algae and other small organisms. They can grind small bits of food. Some species are carnivorous, herbivorous or detritovores.  Sigura alternate is an herbivore.

Life history: Larvae and adults can over winter in ponds. Eggs are laid in large numbers, attached to aquatic plants by a short stalk, in the spring.  Water boatmen produce 1-2 generations per year. Eggs hatch in 1-2 weeks.  There are 5 nymphal instars that last about 1 week each.

Water boatmen are an important food item for many aquatic organisms including bluegill, largemouth bass and black and white crappie.

Some species of water boatmen are very tolerant of pollution. The corixids are the largest group of water bugs containing over 100 species in North America.

These insects have been dried and sold as bird and fish food. In Mexico, the eggs are collected and used as human food.  Un-like other aquatic bugs, water boatmen do not bite.

Notonectidae – back swimmers

            Notonecta  undulate - back swimmer

Description: Back swimmers is 8-17mm in length.

 The body is elongate and convex. Beaks are segmented and stout, reaching to the base of the fore legs. The name comes from its unusual method of swimming upside down. The hind legs are oar-like and covered with swimming hairs. Front legs are adapted for grasping prey or other objects. Similar to water boatmen, hind legs are used like oars. The back swimmers may have colorful patterns on the body. They are frequently found resting with their head down and body at an angle to the water surface.  Back swimmers breathe by breaking the water surface with the abdomen tip. Air is brought into a chamber under the wings as the bug hangs head down at an angle with legs spread. Some species are able to produce sounds through stridulation. They are wide-spread in North America.

Habitat: Back swimmers are common in ponds and other standing water or slow reaches of streams and rivers. Adults are strong flyers and disperse over long distances, often in swarms. They are attracted to lights.

Food habits: The Notonectidae are predaceous and can eat tadpoles and small fish. They feed by sucking body fluids from slow or immobile prey. Notonecta spp. also eats insects, crustaceans and snails.

Life history: Backswimmers over winter in the adult stage. Eggs are glued to aquatic plants or other submerged debris or inserted into plant tissues. Incubation time depends on temperature and species. There are 5 nymphal instars.

They will bite. The bite can be mild or feel like bee sting.

Naucoridae – Creeping water bugs

            Pelocoris femoratus - creeping water bug

Description: Creeping water bugs are brownish, oval, and flattened. They are about 6-15 mm long with broad, stout, raptorial front fore legs terminating in a single claw. Creeping water bugs are similar in shape to giant water bugs. They can be distinguished from them by lack of veins in the membranous area of each wing cover. They have fully developed wings but seldom fly and they are able to swim as well as crawl.

Habitat: The creeping water bug lives in quiet water and creeps about through submerged vegetation. Pelocorus spp. are most common in ponds.

Food habits: The creeping water bug feeds on other insects and small aquatic animals

Life history: Eggs are gray colored and oval. They are glued to rocks and pebbles in shallow water. Larval stages resemble the adult. Winter is passed in the adult stage. An air bubble on the ventral side of the insect provides for respiration underwater.  Dissolved oxygen from the water can continually enter the air bubble allowing the creeping water bug to remain submerged almost indefinitely. They are quick to bite, and the bite is painful. There are 20 species and 5 genera in North America.

 Belostomatidae – Giant water bugs

 

Giant water bug Lethocerus americanusBellostoma flumineum

 

 

 

 

 

 

 

 

 

 

Giant water bug                               Giant water bug Lethocerus americanus

Bellostoma flumineum                   

Description: Giant water bugs are the largest bugs in the order Hemiptera, 20-65 mm.  Fore legs are raptorial with 1or 2 claws.  Membranous veins are present in the wing covers. Abdomen ends in a pair of terminal short plate like structures in some. Lethocerus is brownish, and flattened into an elongated oval. Bellostoma is olive to black in color.

When handled or removed from water, giant water bugs may feign death for several minutes. They also are known to forcefully expel fluid from the anus when held out of water.

Habitat: Giant water bugs inhabit ponds pools and streams. They conceal themselves among vegetation, sticks or debris. Giant water bug  spend much time hanging from the water surface by the tip of the abdomen. They are attracted to lights and are often called electric light bugs because of this trait.

Food habits: Voracious. The creeping water bug feeds on other insects and small aquatic animals such as tadpoles, snails, small fish and frogs.

Life history:  Belostomatids over winter in the adult stage. Up to 100 eggs are glued on the backs of Bellostoma males on special sticky egg pads. The male carries them until hatched; maintaining an intermittent water flow over the eggs by stroking them with his hind legs. Water flow helps maintain adequate oxygen levels around eggs and helps prevent fungal infections.  Eggs that become dislodged are not likely to hatch and may be cannibalized by the male. Dislodged eggs have little chance of hatching.                                                          

Eggs of Lethocerus are laid in rows attached to aquatic vegetation, sticks or other objects near the water surface.  Egg incubation in the Belostomidae is 1-2 weeks. Nymphal development requires 43-54 days and progresses through 5 instars.

Giant water bugs can give a painful bite. These insects are also known as “toe biters”. Lethocerus is a common food item in Asian markets. The insects are sold canned in various savory sauces or as a dish in local restaurants.

Nepidae – water scorpions

 

 

 

 

 

 

 

 

 

                               

 

 

 

Nepa - Nepa apiculata                               Water scorpion – Ranatra sp.

Description: Nepa apiculata –The body is oval and flattened, Front legs are raptorial. The breathing tube at the abdomen tip is almost as long as the body and is formed from cerci.

Ranatra sp. are similar to Nepa except that they are slender with long legs and a narrow, stick-like body, similar in form to a walking stick. These insects have wings but seldom fly. The Nepidae are poor swimmers. Water scorpions are 15-45 mm in length, not including the breathing tube which can be up to 20 mm in length.  Breathing tubes help distinguish water scorpions from similarly shaped marsh treaders or giant water bugs.  Water scorpions have 3 disc shaped static sense organs located on the ventral side of the thorax. These organs are used to orient the bugs in deep water so they are able to return to the surface for air.

Habitat: The Nepidae are most often found in shallow water, slowly crawling through aquatic vegetation of streams, ponds and swamps in search of prey.

Food habits: Water scorpions are predaceous. They feed on any suitably sized aquatic bugs and various other small aquatic animals. Prey items include mosquito larvae, mayfly nymphs and small crustaceans. Water scorpions do not actively pursue prey. They wait in concealment among vegetation and debris for food organisms to come within reach. Prey are captured with the front legs and pierced by the water scorpions’ sharp beak.

Life history: Eggs are laid during the growing season. Eggs of the water scorpion are inserted into aquatic plant tissue and hatch 2 – 4 weeks later.  The 5 nymphal instars stages last about 1 week each. Water scorpions can make a squeaking noise by rubbing a thickened area of the front coax against the coax cavity. Water scorpions can inflict a painful bite.                                                                                                                      

Gelastocoridae – Toad bugs

          Gelastocoris  oculatus - Toad bug

Description: Toad bugs look and hop like small toads. They are 6-9 mm in length and the body is warty and squat. They have relatively short heads with large protuberant eyes and small concealed antennae. The fore legs are modified for grasping prey.

Habitat: Toad bugs are found around the moist margins of ponds; inhabiting damp sand or mud.

Food habits: Gelastocoris feeds by leaping on small shore dwelling insects and grasping the prey with their stout fore legs.

Life history: Toad bug eggs are laid in sand and hatch in about 12 days. There are 5 nymphal instar stages that resemble adult forms but lack abdominal scent glands. Adults spend a portion of their life in the sand. Nymphs are similar to adult forms The Gelastocoridae are widespread.

Suborder - Amphibicorizae

Gerridae – Water striders

                   Gerris sp. - Water striders

Description: Water striders are long legged insects, 3-20 mm in length.  The body is long, narrow and colored dark grey to black. Fine tarsal hairs are difficult to wet and allow the water strider to stay on the water surface. Winged, partially winged and wingless adults occur in many species. The femurs of the hind legs are usually quite long and always surpass the end of the abdomen. Scent gland secretions from these insects may prevent predation by fish. Water striders may use tapping on the water surface with fore legs as a means of communication or for locating prey.

Habitat: Water striders live the on the surface of shallow, quiet, protected water. They are gregarious and often found in large numbers.

Food habits: Striders are predaceous and feed on aquatic insects or insects that fall on the water surface. They are also cannibalistic. Short front legs are used to capture prey.

Life history: Water striders over winter in the adult stage. Eggs are laid on the surface of the water on floating objects, near the water’s edge, in spring and summer. The long, cylindrical eggs are laid in parallel rows. The egg incubation period is about 2 weeks. There are 5 instars that each last about 1 week before the adult form is attained. There are 40-50 species in North America.  

Hydrometra sp. - Marsh treader

Description: The marsh treader is about 8-11 mm in length, gray in color, very delicate and slender. The head is greatly elongated and legs are slender. Claws are terminal. Marsh treaders may be confused with water scorpions or walking sticks. They are usually wingless.

Habitat: Marsh treaders can be found walking slowly over the aquatic vegetation of quiet, shallow waters. Marsh treaders can walk on the water surface without breaking water surface tension.

Food habits:  Marsh treaders feed on very small aquatic organisms that live in the surface film, insects that fall on the water surface and also scavenge dead insects. Mosquito larvae and ostracods are often found in the diet of these insects.  They lie in wait or slowly stalk their prey. Antennae help to locate food items.

Life history: Adults over winter and lay eggs in the spring. Eggs are about 2 mm long, spindle-shaped and are laid singly attached by a slender stalk to objects near or just above the water surface. Eggs hatch in about 1 week.  There are 5 larval instar stages similar in appearance to the adult forms. There are 9 species of marsh treader in North America.

 

Order Coleoptera –Beetles

   Suborder - Adephaga    

      Dysticidae – Predaceous diving beetles

          Coptotomus lenticus  - Predaceous diving beetle

 

 

 

 

 

 

 

 

 

 

 

Description:   Adults are 3- 40 mm in length. brown, black or greenish or yellowish in color.

Predaceous diving beetles are smooth, oval and hard. Hind legs are flattened and covered in long hairs that aid swimming. Because air is carried in a chamber under the elytra (hard outer wings) they can remain under water for a long time. Some species can get air from bubbles on under water plants.  Air is replenished in the sub-elytral chamber by placing the tip of the abdomen above the water surface. The abdomen tip is covered with oil coated hairs that are not wetted and facilitate air intake into spiracles and the sub-elytral air chamber. Larvae have a pair of abdominal gills on the first 6 segments and do not need to surface to breathe.  Some larval species breathe through the skin. Predaceous diving beetles look somewhat like water scavenger beetles, however, water scavenger beetles have shorter clubbed antennae and a more convex body.  Also, predaceous diving beetles move their hind legs simultaneously while swimming while water scavenger beetles move legs alternately. 

Larvae of the predaceous diving beetle are 5-70 mm in length.  Their abdomen has 8 segments and is tapered at the end.  Mandibles are sickle-shaped and toothless with specialized grooves to extract fluids from prey.

Habitat: Predaceous diving beetles can be found in puddles, turbid ponds or ponds filled with aquatic vegetation. They often hang head downward from the surface into the water Adults are attracted to lights at night. Predaceous diving beetles can be found in almost every kind of aquatic habitat.

Food habits: Adults and larvae are highly active, predaceous and can be cannibalistic. Predaceous diving beetles feed on small animals, tadpoles and fish. They will attack animals much larger than themselves. The Larvae of Dysticus spp. are called “water tigers”. They are equipped with sharp, channeled jaws that pierce prey. Larvae inject the prey with a brown colored fluid that kills and digests the prey. Digested contents of the body are sucked up through the mandibles of the larvae.

Life history: Adults hibernate through the winter. Eggs are laid just out of the water or attached to stems and leaves of under water plants. Eggs hatch according to water temperature and it may take from a week to several months.  There are 3 larval instars. Larvae are worm-like and look much different than the adult. At the third molt the larvae crawl out of the water and burrow into damp soil to form a pupal chamber. Adults leave the pupa 4-6 weeks after forming them. There are about 400 species of predaceous diving beetles and about 35 genera. Largest of the water beetle families. Many species are excellent fliers and adept swimmers..

Gyrinidae – Whirligig beetles

          Gyrinus sp. - Whirlygig beetle

 

 

 

 

 

 

 

 

 

 

 

 

Description: The whirlygig beetle is oval, black and 3-15 mm in length with relatively short mid and hind legs. Front legs are long and used for grasping. Larvae are elongate and up to 30 mm in length. Adult beetles are commonly seen in large swarms spinning about on the water surface. Several different species may sometimes be found in the swarms. Whirlygig beetles have flattened mid and hind legs that rapidly propel the beetles through the water at up to 1 meter per second. Wave reflections off objects may transmit information to the beetles about size and location of objects. Whirlygig beetles have pairs of eyes on upper and lower sides of the head. They dive, swim erratically and emit foul smelling secretions if disturbed. Dineutus spp. release a milky colored secretion smelling like ripe apples or pears if disturbed. Species of Gyrinus have an offensive odor. Secretions are distasteful and provide some defense against predation.

Although mostly a surface dweller, gyrinids can dive below the surface of the water when frightened or laying eggs. Air is stored under the elytra and an air bubble is formed on the hairy tip of the abdomen.

Larvae can be distinguished by rings of lateral gill projections on abdominal segments and the posterior.  Abdominal segments are undulated to provide a water current over the gill structures.

Habitat: Whirlygig beetles are the only beetle able to live on the water surface. They can be found in ponds and streams in quiet areas and are wide spread and abundant. Most species are usually diurnal.

Food habits:  Larvae and adults are predaceous. Adults feed on insects that fall on the water surface or scavenge bits of floating organic material. Larvae are predaceous and cannibalistic. They eat blood worms, insect larvae and other aquatic organisms. Larvae inject poison into prey through a canal located in their mandibles.

Life history: Whirlygig beetles lay eggs in rows or clusters attached to submerged plants in spring. Eggs hatch in 1-3 weeks. Larvae drop off plants and feed among debris on the pond bottom. Mature whirligig beetle larvae crawl out of the water onto plants, stones or other objects where they construct a pupal cocoon of plant matter and sand grains.  

Suborder Polyphaga

Hydrophilidae – Water scavenger beetles

                   Hydrophilus sp. - Water scavenger beetle

 

 

 

 

 

 

 

 

 

 

 

 

 

Description: Water scavenger beetles are black to very dark green in color, oval, convex and up to 40mm  long. They have short clubbed antennae and long maxillary palps. The subfamily Hydrophilinae have a distinct ventral spine or keel that can be used to jab into the fingers of careless handlers. Unlike the similar looking predaceous diving beetles, water scavenger beetles rarely hang with head down under the water.  Also, unlike predaceous diving beetles, water scavenger beetles swims with an alternate motion of the hind legs. Air is carried underwater in a silvery film on the ventral side of the beetle. 

Larvae mandibles are strong and usually have 1 or more teeth .Larvae may appear wrinkled.

Habitat: Water scavenger beetles live in ponds and shallow regions of lakes. They are also found in quieter waters of streams and rivers.

Food habits:  Adults are omnivorous scavengers, mainly herbivorous but will eat dead animal matter.

Larvae are predaceous and cannibalistic. They feed on a variety of small aquatic animals

Life history: Adults fly well. Dispersal flights occur in spring and August and September. Many species are attracted to lights. Eggs are usually laid in spring in silken cases attached to aquatic plants by a flexible strand. There are three larval instars before larvae pupate. Larvae leave the water and pupate in underground cells in damp soil. There are over 200 aquatic species. Adults and larvae are a food source for many aquatic animals including ducks, wading birds, frogs, toads and fish.

Culicidae - Mosquitoes

    Culex pipiens. - Common house mosquito

 

 

 

 

 

 

Description: Larvae are 3-15 mm. in length, cylindrical, and white to gray in color. They breathe through an angled breathing tube that pierces the water surface.  There are several pairs of hair tufts on the breathing tube. Resting larvae hold the body at an angle to the surface. 

Adults are 4-5 mm long and have mouth parts formed into a long proboscis. Wings are held flat over body. Scales are located along wing veins.

Habitat: Culex spp. are found in a wide variety of standing water, tin cans and tree stumps to quiet areas of lakes.

Food habits: larvae feed on algae, organic detritus and floating or suspended microorganisms.  Male adults feed on nectar from plants Females are blood feeders.  Most species feed at night or twilight. Some attack during the daylight hours. Some species swarm.

Life history: Culex spp   eggs are laid in rafts on the  water surface.  Eggs hatch into larvae called “wrigglers”. Larvae develop into Pupae known as “tumblers”.  The pupal stage is aquatic and active. Pupae breathe at the water surface through a pair of small funnel-like structures on the thorax. Culex spp. produce several generations per year.  Mosquitos are vectors of several important diseases including yellow fever, dengue fever, malaria, filariasis and some types of enchepalitis.  There are approximately 12 genera and 150 mosquito species in North America.

Chironomidae – midges

          Chironomus sp. - Blood worm

 

 

 

 

 

 

Description: Blood worms are 2-20 mm length. Larvae of some species are red due to haemoglobin in blood. Haemoglobin may allow the larvae to live under anaerobic or very low oxygen level conditions. Larvae have a pair of anterior and posterior prolegs.  Adults are about 10 mm long and often occur in large swarms, usually in the evening.  The swarms make a humming sound. Adult midges look like small pale mosquitoes.  Females lack the bristling antennae found on the male. Most species build cases made of sand or other substrate material cemented together with saliva.

Habitat:  Midges are found in most aquatic environments. Larvae are bottom dwelling and can be dominant in the sub-littoral and profundal zones. Chironomus sp. bloodworms can live in highly polluted, eutrophic waters.

Food habits:  Larvae are scavengers.

Life history: There may be one to several generations per year depending on water temperature and species. Larvae live in the pond ooze and pupate in larval tunnels. Pupae float to the surface just before the adult emerges. The midge family is a large group containing over 100 genera and about 670 species.  They are frequently abundant and are perhaps the most important food item for many species of fish and other aquatic animals.

References:

An Introduction to the Study of Insects. 4th Edition, Borror  Donald J., DeLong Dwight M. and Triplehorn Charles A. Holt Rinehart and Winston1976.

Aquatic Entomology. W. Patrick McCafferty. Illustrations by Arwin V Provonsha.Jones and Bartlett Publishers 1998.

Aquatic Insects of California,  Edited by Robert L. Usinger, Univ. Calif. Press 1956.

 

 

 

 

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