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True Bugs
Chapter 23
True Bugs: Insect Order Hemiptera I. INTRODUCTION TO THE ORDER HEMIPTERA Contrary to the vernacular spoken routinely by the average person on the street—and even casually by most aquatic ecologists—all insects are not bugs! Indeed, there is a large taxonomic group of true bugs, but the name and taxonomic relationships of this group are frequently disputed by entomologists. In that regard, we follow here recommendations in the Tree of Life project (http:// tolweb.org/Hemiptera) to classify true bugs as the suborder Heteroptera in the order Hemiptera. This order contains a diverse mixture of groups, including aphids, cicadas, and true bugs. All freshwater hemipterans are also heteropterans, and all share the ordinal feature of having specia lized elongated mouthparts useful for sucking fluids from other organisms. Through the remainder of this chapter “aquatic bugs” or just “bugs” will refer to freshwater members of the suborder Heteroptera. Of the roughly 38,000 described species of heteropterans around the world, a little under 9% are aquatic and have nymphs and adults that live in the water (the majority) or on its surface, usually in nonflowing habitats. The surface-dwelling species are sometimes categorized as “semiaquatic.” At least 412 species of aquatic bugs have been described from North America, but relatively little attention has been given to this group over the last half century so many other species may exist. Adults are fairly easy to identify even in the field, but classifying nymphs is more challenging even at the generic level. Aquatic bugs are harmless unless picked up, but some species can produce a temporary but painful “bite” when their proboscis pierces an incautiously grasping hand—which has happened to the authors more than once! Some biting bugs, such as backswimmers (Notonectidae) and giant water bugs (Belostomatidae) are occasionally pests in swimming pools when accidentally encountering humans. From a more serious economic standpoint, members of the belostomatid genus Lethocerus, sometimes called “toe bitters,” can wreak havoc in fish hatcheries. These and other large bugs will also kill small fish in home aquaria. The reason for this occasional negative impact on humans is that nymphs and adults of many species are predators. This feeding mode also benefits humans because larval mosquitoes and other biting flies are preyed upon by aquatic bugs. Humans also benefit from aquatic bugs because various species are considered a food delicacy in some parts of the world, including Mexico and some Asian countries, and some taxa like water boatmen (Corixidae; Fig. 23a) are marketed as dry food for pet turtles and aquarium fish. The presence of large numbers of aquatic bugs is sometimes an indicator of water pollution. Although they are not necessarily more resistant to toxins than other insects, they avoid problems encountered by other aquatic insects under polluted, low oxygen levels because most bugs obtain their oxygen directly from the atmosphere rather than from dissolved supplies. © 2011 Elsevier Inc. All rights reserved.
ISBN 978-0-12-381426-5, DOI: 10.1016/B978-0-12-381426-5.00023-5
205
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Field Guide to Freshwater Invertebrates of North America
FIG. 23A. A genus of water boatmen, Hesperocorixa.
II. FORM AND FUNCTION A. Anatomy and Physiology Aquatic bugs can be identified by their highly modified mouthparts which are shaped into a tube-like rostrum used to suck liquified prey tissue into the bug’s body. This rostrum projects down, below, and behind the head. In addition, the overlapping fore wings of adults are hardened at the basal half and membranous closer to the tips. The shorter hind wings of the adults are entirely membranous and held beneath the larger hind wings and over the abdomen. Nymphs have partially developed wings, called wing pads. There are some differences between the leg structure of nymphs and adults, but these are not easily seen without a microscope. In some species, one or more pairs of legs have paired terminal claws. The body shape varies dramatically among species from flattened ovals (e.g., creeping water bug, Naucoridae) to slender and highly elongated shapes (e.g., water scorpions, Nepidae). Most are in the size range of 20–60 mm, but some giant water bugs reach 100 mm! The strategies of aquatic bugs for obtaining oxygen differ markedly from other aquatic insects. All species of bugs lack external gills and rely instead on internal respiratory tubes (tracheae). When oxygen is needed by surface-dwelling species, they need only open their spiracles covering the entrance to the tracheae. Submerged species, however, follow one of two strategies. Most species travel to the surface and either expose their tracheae to the atmosphere or stick a breathing tube through the surface film, much like the snorkel used by skin divers. Other bugs carry a bubble of air on their ventral side which provides oxygen to the tracheae. Either this bubble is replenished occasionally from the water surface or, in less active species, oxygen diffuses from the water into the bubble as levels drop creating a diffusion gradient in favor of the bug.
B. Reproduction and Life History The typical 1-year life history pattern for aquatic bugs involves egg laying in the spring, nymph development through four to five instars to adults during warmer months of summer and early fall, overwintering as adults, and mating in the late winter or spring. Eggs are secured on aquatic plants or other solid objects within the water or are placed just above the water by some semiaquatic bugs. The average time spent as a nymph is about 2 months, but ranges from 1 to 8 months depending on the species and location. In more rigorous environments, such as in northern latitudes, adults of semiaquatic species may hibernate in protective microhabitats of mud or leaves. (Hibernation differs from the diapause of other species in that full development has already occurred in the former state.) Dispersal among habitats occurs in the adult phase, but bugs usually disperse only when local conditions deteriorate. This three-stage, paurometabolous cycle (egg, larva/nymph, and adult) differs
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True Bugs: Insect Order Hemiptera
from the three-stage hemimetabolous cycle of mayflies, dragonflies, and stoneflies in that the adults and nymphs of bugs differ very little in structure and they live in the same environment.
III. ECOLOGY, BEHAVIOR, AND ENVIRONMENTAL BIOLOGY A. Habitats and Environmental Limits The morphology and habits of aquatic bugs make them less suited for turbulent habitats, and thus most species occur in calmer waters of ephemeral pools through shorelines of large lakes. They also occur in some salt lakes and ponds. Few species venture far from this habitat. Those found in creeks through large rivers occur almost exclusively in pools, lateral slack waters, and/or among protected aquatic weeds. Nymphs and adults colonize very similar habitats and are typically intermixed with each other.
FIG. 23B. A member of the water strider family Gerridae.
Most aquatic bugs climb, swim, or “row” (e.g., water boatmen and backswimmers) among aquatic vegetation in lentic and lotic habitats, probably because of food availability and reduced preda tion. Examples of these are giant water bugs, creeping water bugs, and water scorpions. The semiaquatic bugs, such as water striders (Gerridae; Fig. 23b) and water treaders (Mesoveliidae), skate across the surface on hydrophobic legs in search of trapped prey or insects within diving distance. Finally, a few taxa, such as water boatmen seek food near the undersurface of the air–water interface. Although the coverage of this book is confined to inland waters, it is interesting to note that some species of water striders live on the surface of the open ocean in the absence of all other insects!
B. Functional Roles in the Ecosystem and Biotic Interactions The adults and nymphs of many species of aquatic bugs are predators, with most species feeding on a variety of invertebrate prey including mosquito larvae and aquatic bugs of the same or different species. Large species will attack larval fish of most species and the adults of smaller fish taxa like minnows. Giant water bugs have also been observed successfully attacking tadpoles, small frogs, salamanders, and crustaceans of modest size. The fore legs of bugs are generally equipped to grasp and hold struggling prey. The hind legs may be used in propulsion or for grasping a stable surface while waiting for a passing prey. Once the prey has been secured, the rostrum injects toxic enzymes which first paralyze and then digest the prey (within the prey’s body) before the liquified contents are sucked into the bug’s digestive tract for further digestion. This technique allows the bug to kill an organism up to 50 times its size in some cases. Water boatmen are one of the few aquatic bugs that include some nonpredaceous species in the family. Many of these common bugs are instead collector-gatherers, feeding on algae and detritus in suspension or at the water surface. Like many terrestrial species, such as the “stink bug,” many aquatic bugs have scent glands which seem to repel some predators. Those bugs lacking this deterrent, such as water boatmen, are subject to more intense predation from some fish but especially from resident and migratory birds.
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C. Stridulation Many male true bugs stridulate. This is accomplished by rubbing together a specialized row or small ridges on one surface (called a strigil) and one or more rows on another surface. The result is a squeaking sound. Stridulation is used to attract mates. In the water boatmen the strigil is on the abdomen, whereas in the backswimmers it is on the front legs. Sometimes these animals will stridulate when they become alarmed, so do not be surprised if you capture a true bug and it begins squeaking in protest!
IV. COLLECTION AND CULTURING Aquatic bugs can be collected from lentic or sometimes lotic habitats. In the former, the bugs can be found in submerged vegetation throughout the wetlands and near the shoreline among weeds of ponds and lakes. You can also collect them from the water surface of these habitats. In streams, aquatic bugs occur in sluggish waters, including stream pools and lateral channels with minimal or zero currents, or in thick vegetation in slow flowing areas of river swamps. When seeking fully aquatic species, use a D-net to scoop up rooted vegetation and place it in an observation pan. If you are not wearing gloves, watch out for hidden bugs that will strike if cornered while you are scooping or sorting vegetation. When seeking semiaquatic, surface bugs, a quick pounce and sweep with a D-net or even a stout butterfly net will work (though it is easy to tear the more delicate mesh). A problem for the human collector is that semiaquatic species are very wary and are watchful for both bird and fish predators, so it can be difficult to get one with a single sweep. Maintaining aquatic bugs in an aquarium is relatively easy as long as you provide submerged physical structure, adequate live prey, a habitat lacking fish predators, and an escape-proof aquarium (nymphs crawl or swim very well and adults can fly). Getting adequate prey and making the aquarium “de-bug proof” will be the hardest tasks. If you want to preserve aquatic bugs you can either put them in an tightly capped jar with alcohol (see Chapter 2) or you can dry some specimens of mostly semiaquatic species (or the larger submerged species) following techniques you would employ for terrestrial insect specimens.
Chapter | 23
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True Bugs: Insect Order Hemiptera
V. REPRESENTATIVE TAXA OF TRUE BUGS: ORDER HEMIPTERA A. Shore Bugs (Fig. 23c): Saldidae, Ochteridae Identification: Oval dark brown to black bugs, sometimes with white speckles or mottling. Often running or jumping. Very quick to fly away. Size: 4–7 mm. Range: Widespread in North America outside of the arctic regions. Habitat: Shorelines of permanent or temporary habitats, some times on rocks, mud, or sand. Never on open water. Remarks: These insects are predators and scavengers, and they can leap several times their own body length.
B. Toad Bugs (Fig. 23d): Gelastocoridae Identification: Round, flat bodied, jump ing bugs. Gray, brown, or black with mottles of white or gray. Size: 4–9 mm. Range: Widespread in North America outside of the arctic regions. Habitat: Shorelines of permanent or temporary habitats, sometimes on rocks, mud, or sand. Never on open water. Remarks: These insects are predators. Some species burrow in sand.
C. Water Treaders, Velvet Water Bugs, Riffle Bugs, Water Crickets (Fig. 23e): Hebridae, Mesoveliidae, Macroveliidae, Veliidae Identification: Oblong to triangular dark brown to black bugs, sometimes with white margins, or lighter abdomens. Often occurring in very large groups. Size: 3–7 mm. Range: Widespread in North America south of the arctic regions. Habitat: On the water surface at or near shorelines, sometimes on rocks, or on vegetation of permanent habitats. Remarks: These insects are pre dators or scavengers. Some species are flightless.
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D. Water Measurers (Fig. 23f): Hydrometridae Identification: Long thin, stick or hairlike insects, with thread like legs. Light brown to beige. Size: 4–11 mm. Range: Widespread in North America. Habitat: In quiet permanent water, in well-vegetated areas, or under overhan ging banks. Remarks: These insects are predators. Most species lack wings or have reduced winged forms.
E. Water Striders, Water Skippers (Fig. 23g): Gerridae Identification: Elongated or round bod ied, dark brown to black bugs, with a white or silver underside. The middle and hind leg pairs are elongated. Size: 4–20 mm. Range: Widespread in North America outside of the arctic regions. Habitat: Skating along on the open water surface in any quiet or slow-flow ing waters. Remarks: These insects are predators and scavengers. Some species are wingless.
Chapter | 23
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True Bugs: Insect Order Hemiptera
F. Pygmy Backswimmers (Fig. 23h): Pleidae Identification: Humpbacked, round bod ied, upside down swimming bugs, with the hind leg pair elongated for swim ming. Color is brown to cream with brown patterning. Size: 1.9–2.25 mm. Range: North America east of the con tinental divide in warmer regions, as far north as Ontario and Quebec, and extend ing west and north into Idaho and Mani toba. Habitat: Well-vegetated ponds, lakes, and rivers. Remarks: These insects are predators.
G. Backswimmers (Fig. 23i): Notonectidae Identification: Streamlined, cylindrical or round bodied, upside down swimming bugs, with the hind leg pair elongated for swimming. The underside is black or white, but the dorsal surface may be black, white, yellow, or crimson. Size: 5–20 mm. Range: Widespread in North America. Habitat: Any quiet or slowflowing aquatic habitat. Remarks: These insects are predators and can give a sharp bite. They will sometimes squeak.
H. Boatmen, Water Boatmen, Oarsmen (Fig. 23j): Corixidae Identification: Streamlined, flat bodied, right side up swimming bugs, with the hind leg pair elongated for swimming. The underside is cream or white, some times black. The dorsal surface may be black, white, gray, or yellow with various markings. Size: 5–20 mm. Range: Wide spread in North America. Habitat: Any quiet or slow-flowing aquatic habitat. Remarks: These insects are herbivores and will not bite. They will sometimes squeak.
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Field Guide to Freshwater Invertebrates of North America
I. Creeping Waterbugs, Toebiters (Fig. 23k): Naucoridae Identification: Round, flat bodied, swimming bugs, with sharp, rigid front legs. May be green, brown, or yellow. Size: 4–10 mm. Range: Widespread in North America south of the arctic and subarctic regions. Habitat: Permanent ponds, lakes, streams, and rivers. Typi cally in vegetation or algae. Remarks: These insects are predators and can give a painful bite.
J. Giant Waterbugs, Toebiters, Electric Light Bugs (Fig. 23l): Belostomatidae Identification: Large, flat bodied, swim ming bugs, with strong front legs. Always brown. Females often lay their eggs on the male’s back. Size: 12– 60 mm. Range: Widespread in temperate and subtropical North America. Habitat: Permanent or temporary ponds and lakes. Typically in vegetation, rarely in open water. Remarks: These insects are pre dators and can give a painful bite. They sometimes come to lights in large numbers.
K. Water Scorpions (Fig. 23m): Nepidae Identification: Large, flat or cylindrical, elongated bugs, with long legs and a pair of long breathing tubes projecting from the tail. Always brown. Poor swimmers. Size: 12–100 mm. Range: Widespread in temperate and subtropical North Amer ica. Habitat: Permanent or temporary ponds and lakes, slow streams, and springs. Typically in vegetation. Remarks: These insects are predators and can give a painful bite. They are poor swimmers and rely on camouflage to capture their prey.
True Bugs: Insect Order Hemiptera I. INTRODUCTION TO THE ORDER HEMIPTERA Contrary to the vernacular spoken routinely by the average person on the street—and even casually by most aquatic ecologists—all insects are not bugs! Indeed, there is a large taxonomic group of true bugs, but the name and taxonomic relationships of this group are frequently disputed by entomologists. In that regard, we follow here recommendations in the Tree of Life project (http:// tolweb.org/Hemiptera) to classify true bugs as the suborder Heteroptera in the order Hemiptera. This order contains a diverse mixture of groups, including aphids, cicadas, and true bugs. All freshwater hemipterans are also heteropterans, and all share the ordinal feature of having specia lized elongated mouthparts useful for sucking fluids from other organisms. Through the remainder of this chapter “aquatic bugs” or just “bugs” will refer to freshwater members of the suborder Heteroptera. Of the roughly 38,000 described species of heteropterans around the world, a little under 9% are aquatic and have nymphs and adults that live in the water (the majority) or on its surface, usually in nonflowing habitats. The surface-dwelling species are sometimes categorized as “semiaquatic.” At least 412 species of aquatic bugs have been described from North America, but relatively little attention has been given to this group over the last half century so many other species may exist. Adults are fairly easy to identify even in the field, but classifying nymphs is more challenging even at the generic level. Aquatic bugs are harmless unless picked up, but some species can produce a temporary but painful “bite” when their proboscis pierces an incautiously grasping hand—which has happened to the authors more than once! Some biting bugs, such as backswimmers (Notonectidae) and giant water bugs (Belostomatidae) are occasionally pests in swimming pools when accidentally encountering humans. From a more serious economic standpoint, members of the belostomatid genus Lethocerus, sometimes called “toe bitters,” can wreak havoc in fish hatcheries. These and other large bugs will also kill small fish in home aquaria. The reason for this occasional negative impact on humans is that nymphs and adults of many species are predators. This feeding mode also benefits humans because larval mosquitoes and other biting flies are preyed upon by aquatic bugs. Humans also benefit from aquatic bugs because various species are considered a food delicacy in some parts of the world, including Mexico and some Asian countries, and some taxa like water boatmen (Corixidae; Fig. 23a) are marketed as dry food for pet turtles and aquarium fish. The presence of large numbers of aquatic bugs is sometimes an indicator of water pollution. Although they are not necessarily more resistant to toxins than other insects, they avoid problems encountered by other aquatic insects under polluted, low oxygen levels because most bugs obtain their oxygen directly from the atmosphere rather than from dissolved supplies. © 2011 Elsevier Inc. All rights reserved.
ISBN 978-0-12-381426-5, DOI: 10.1016/B978-0-12-381426-5.00023-5
205
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Field Guide to Freshwater Invertebrates of North America
FIG. 23A. A genus of water boatmen, Hesperocorixa.
II. FORM AND FUNCTION A. Anatomy and Physiology Aquatic bugs can be identified by their highly modified mouthparts which are shaped into a tube-like rostrum used to suck liquified prey tissue into the bug’s body. This rostrum projects down, below, and behind the head. In addition, the overlapping fore wings of adults are hardened at the basal half and membranous closer to the tips. The shorter hind wings of the adults are entirely membranous and held beneath the larger hind wings and over the abdomen. Nymphs have partially developed wings, called wing pads. There are some differences between the leg structure of nymphs and adults, but these are not easily seen without a microscope. In some species, one or more pairs of legs have paired terminal claws. The body shape varies dramatically among species from flattened ovals (e.g., creeping water bug, Naucoridae) to slender and highly elongated shapes (e.g., water scorpions, Nepidae). Most are in the size range of 20–60 mm, but some giant water bugs reach 100 mm! The strategies of aquatic bugs for obtaining oxygen differ markedly from other aquatic insects. All species of bugs lack external gills and rely instead on internal respiratory tubes (tracheae). When oxygen is needed by surface-dwelling species, they need only open their spiracles covering the entrance to the tracheae. Submerged species, however, follow one of two strategies. Most species travel to the surface and either expose their tracheae to the atmosphere or stick a breathing tube through the surface film, much like the snorkel used by skin divers. Other bugs carry a bubble of air on their ventral side which provides oxygen to the tracheae. Either this bubble is replenished occasionally from the water surface or, in less active species, oxygen diffuses from the water into the bubble as levels drop creating a diffusion gradient in favor of the bug.
B. Reproduction and Life History The typical 1-year life history pattern for aquatic bugs involves egg laying in the spring, nymph development through four to five instars to adults during warmer months of summer and early fall, overwintering as adults, and mating in the late winter or spring. Eggs are secured on aquatic plants or other solid objects within the water or are placed just above the water by some semiaquatic bugs. The average time spent as a nymph is about 2 months, but ranges from 1 to 8 months depending on the species and location. In more rigorous environments, such as in northern latitudes, adults of semiaquatic species may hibernate in protective microhabitats of mud or leaves. (Hibernation differs from the diapause of other species in that full development has already occurred in the former state.) Dispersal among habitats occurs in the adult phase, but bugs usually disperse only when local conditions deteriorate. This three-stage, paurometabolous cycle (egg, larva/nymph, and adult) differs
Chapter | 23
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True Bugs: Insect Order Hemiptera
from the three-stage hemimetabolous cycle of mayflies, dragonflies, and stoneflies in that the adults and nymphs of bugs differ very little in structure and they live in the same environment.
III. ECOLOGY, BEHAVIOR, AND ENVIRONMENTAL BIOLOGY A. Habitats and Environmental Limits The morphology and habits of aquatic bugs make them less suited for turbulent habitats, and thus most species occur in calmer waters of ephemeral pools through shorelines of large lakes. They also occur in some salt lakes and ponds. Few species venture far from this habitat. Those found in creeks through large rivers occur almost exclusively in pools, lateral slack waters, and/or among protected aquatic weeds. Nymphs and adults colonize very similar habitats and are typically intermixed with each other.
FIG. 23B. A member of the water strider family Gerridae.
Most aquatic bugs climb, swim, or “row” (e.g., water boatmen and backswimmers) among aquatic vegetation in lentic and lotic habitats, probably because of food availability and reduced preda tion. Examples of these are giant water bugs, creeping water bugs, and water scorpions. The semiaquatic bugs, such as water striders (Gerridae; Fig. 23b) and water treaders (Mesoveliidae), skate across the surface on hydrophobic legs in search of trapped prey or insects within diving distance. Finally, a few taxa, such as water boatmen seek food near the undersurface of the air–water interface. Although the coverage of this book is confined to inland waters, it is interesting to note that some species of water striders live on the surface of the open ocean in the absence of all other insects!
B. Functional Roles in the Ecosystem and Biotic Interactions The adults and nymphs of many species of aquatic bugs are predators, with most species feeding on a variety of invertebrate prey including mosquito larvae and aquatic bugs of the same or different species. Large species will attack larval fish of most species and the adults of smaller fish taxa like minnows. Giant water bugs have also been observed successfully attacking tadpoles, small frogs, salamanders, and crustaceans of modest size. The fore legs of bugs are generally equipped to grasp and hold struggling prey. The hind legs may be used in propulsion or for grasping a stable surface while waiting for a passing prey. Once the prey has been secured, the rostrum injects toxic enzymes which first paralyze and then digest the prey (within the prey’s body) before the liquified contents are sucked into the bug’s digestive tract for further digestion. This technique allows the bug to kill an organism up to 50 times its size in some cases. Water boatmen are one of the few aquatic bugs that include some nonpredaceous species in the family. Many of these common bugs are instead collector-gatherers, feeding on algae and detritus in suspension or at the water surface. Like many terrestrial species, such as the “stink bug,” many aquatic bugs have scent glands which seem to repel some predators. Those bugs lacking this deterrent, such as water boatmen, are subject to more intense predation from some fish but especially from resident and migratory birds.
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Field Guide to Freshwater Invertebrates of North America
C. Stridulation Many male true bugs stridulate. This is accomplished by rubbing together a specialized row or small ridges on one surface (called a strigil) and one or more rows on another surface. The result is a squeaking sound. Stridulation is used to attract mates. In the water boatmen the strigil is on the abdomen, whereas in the backswimmers it is on the front legs. Sometimes these animals will stridulate when they become alarmed, so do not be surprised if you capture a true bug and it begins squeaking in protest!
IV. COLLECTION AND CULTURING Aquatic bugs can be collected from lentic or sometimes lotic habitats. In the former, the bugs can be found in submerged vegetation throughout the wetlands and near the shoreline among weeds of ponds and lakes. You can also collect them from the water surface of these habitats. In streams, aquatic bugs occur in sluggish waters, including stream pools and lateral channels with minimal or zero currents, or in thick vegetation in slow flowing areas of river swamps. When seeking fully aquatic species, use a D-net to scoop up rooted vegetation and place it in an observation pan. If you are not wearing gloves, watch out for hidden bugs that will strike if cornered while you are scooping or sorting vegetation. When seeking semiaquatic, surface bugs, a quick pounce and sweep with a D-net or even a stout butterfly net will work (though it is easy to tear the more delicate mesh). A problem for the human collector is that semiaquatic species are very wary and are watchful for both bird and fish predators, so it can be difficult to get one with a single sweep. Maintaining aquatic bugs in an aquarium is relatively easy as long as you provide submerged physical structure, adequate live prey, a habitat lacking fish predators, and an escape-proof aquarium (nymphs crawl or swim very well and adults can fly). Getting adequate prey and making the aquarium “de-bug proof” will be the hardest tasks. If you want to preserve aquatic bugs you can either put them in an tightly capped jar with alcohol (see Chapter 2) or you can dry some specimens of mostly semiaquatic species (or the larger submerged species) following techniques you would employ for terrestrial insect specimens.
Chapter | 23
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True Bugs: Insect Order Hemiptera
V. REPRESENTATIVE TAXA OF TRUE BUGS: ORDER HEMIPTERA A. Shore Bugs (Fig. 23c): Saldidae, Ochteridae Identification: Oval dark brown to black bugs, sometimes with white speckles or mottling. Often running or jumping. Very quick to fly away. Size: 4–7 mm. Range: Widespread in North America outside of the arctic regions. Habitat: Shorelines of permanent or temporary habitats, some times on rocks, mud, or sand. Never on open water. Remarks: These insects are predators and scavengers, and they can leap several times their own body length.
B. Toad Bugs (Fig. 23d): Gelastocoridae Identification: Round, flat bodied, jump ing bugs. Gray, brown, or black with mottles of white or gray. Size: 4–9 mm. Range: Widespread in North America outside of the arctic regions. Habitat: Shorelines of permanent or temporary habitats, sometimes on rocks, mud, or sand. Never on open water. Remarks: These insects are predators. Some species burrow in sand.
C. Water Treaders, Velvet Water Bugs, Riffle Bugs, Water Crickets (Fig. 23e): Hebridae, Mesoveliidae, Macroveliidae, Veliidae Identification: Oblong to triangular dark brown to black bugs, sometimes with white margins, or lighter abdomens. Often occurring in very large groups. Size: 3–7 mm. Range: Widespread in North America south of the arctic regions. Habitat: On the water surface at or near shorelines, sometimes on rocks, or on vegetation of permanent habitats. Remarks: These insects are pre dators or scavengers. Some species are flightless.
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Field Guide to Freshwater Invertebrates of North America
D. Water Measurers (Fig. 23f): Hydrometridae Identification: Long thin, stick or hairlike insects, with thread like legs. Light brown to beige. Size: 4–11 mm. Range: Widespread in North America. Habitat: In quiet permanent water, in well-vegetated areas, or under overhan ging banks. Remarks: These insects are predators. Most species lack wings or have reduced winged forms.
E. Water Striders, Water Skippers (Fig. 23g): Gerridae Identification: Elongated or round bod ied, dark brown to black bugs, with a white or silver underside. The middle and hind leg pairs are elongated. Size: 4–20 mm. Range: Widespread in North America outside of the arctic regions. Habitat: Skating along on the open water surface in any quiet or slow-flow ing waters. Remarks: These insects are predators and scavengers. Some species are wingless.
Chapter | 23
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True Bugs: Insect Order Hemiptera
F. Pygmy Backswimmers (Fig. 23h): Pleidae Identification: Humpbacked, round bod ied, upside down swimming bugs, with the hind leg pair elongated for swim ming. Color is brown to cream with brown patterning. Size: 1.9–2.25 mm. Range: North America east of the con tinental divide in warmer regions, as far north as Ontario and Quebec, and extend ing west and north into Idaho and Mani toba. Habitat: Well-vegetated ponds, lakes, and rivers. Remarks: These insects are predators.
G. Backswimmers (Fig. 23i): Notonectidae Identification: Streamlined, cylindrical or round bodied, upside down swimming bugs, with the hind leg pair elongated for swimming. The underside is black or white, but the dorsal surface may be black, white, yellow, or crimson. Size: 5–20 mm. Range: Widespread in North America. Habitat: Any quiet or slowflowing aquatic habitat. Remarks: These insects are predators and can give a sharp bite. They will sometimes squeak.
H. Boatmen, Water Boatmen, Oarsmen (Fig. 23j): Corixidae Identification: Streamlined, flat bodied, right side up swimming bugs, with the hind leg pair elongated for swimming. The underside is cream or white, some times black. The dorsal surface may be black, white, gray, or yellow with various markings. Size: 5–20 mm. Range: Wide spread in North America. Habitat: Any quiet or slow-flowing aquatic habitat. Remarks: These insects are herbivores and will not bite. They will sometimes squeak.
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Field Guide to Freshwater Invertebrates of North America
I. Creeping Waterbugs, Toebiters (Fig. 23k): Naucoridae Identification: Round, flat bodied, swimming bugs, with sharp, rigid front legs. May be green, brown, or yellow. Size: 4–10 mm. Range: Widespread in North America south of the arctic and subarctic regions. Habitat: Permanent ponds, lakes, streams, and rivers. Typi cally in vegetation or algae. Remarks: These insects are predators and can give a painful bite.
J. Giant Waterbugs, Toebiters, Electric Light Bugs (Fig. 23l): Belostomatidae Identification: Large, flat bodied, swim ming bugs, with strong front legs. Always brown. Females often lay their eggs on the male’s back. Size: 12– 60 mm. Range: Widespread in temperate and subtropical North America. Habitat: Permanent or temporary ponds and lakes. Typically in vegetation, rarely in open water. Remarks: These insects are pre dators and can give a painful bite. They sometimes come to lights in large numbers.
K. Water Scorpions (Fig. 23m): Nepidae Identification: Large, flat or cylindrical, elongated bugs, with long legs and a pair of long breathing tubes projecting from the tail. Always brown. Poor swimmers. Size: 12–100 mm. Range: Widespread in temperate and subtropical North Amer ica. Habitat: Permanent or temporary ponds and lakes, slow streams, and springs. Typically in vegetation. Remarks: These insects are predators and can give a painful bite. They are poor swimmers and rely on camouflage to capture their prey.