encyclopedia of inland waters || hemiptera (true bugs)

Hemiptera (True Bugs)J T Polhemus, Colorado Entomological Institute, Englewood, CO, USA

ã 2009 Elsevier Inc. All rights reserved.

General Aspects of Aquatic Heteroptera
Introduction
The Hemiptera are divided here into two suborders,although some consider the Heteroptera to be anorder, and the Homoptera to be a separate order.The suborder Homoptera is being divided; howeverthe classification is not yet settled, so the suborder‘Homoptera’ is retained here for practical reasons. TheHomoptera have not adapted to truly aquatic life ashave many Heteroptera; however some are margin-ally semiaquatic (e.g., Cicadellidae and Delphacidae),inhabiting the margins of freshwaters and feeding onaquatic plants.The aquatic and semiaquatic Heteroptera (‘aquatic

Heteroptera’) are separated from the Homopteraby the mouth parts arising from the front of thehead (Plate I). There are three monophyletic infra-orders, Leptopodomorpha, Gerromorpha, and Nepo-morpha, with worldwide distribution. These representa significant component of the world’s aquatic insectbiota. At present, these three infraorders hold24 families, 343 genera, and 4799 species group taxaconsidered valid, of which 21 families, 323 genera, and4656 species inhabit inland waters. In addition, morethan 1100 unequivocally diagnosed species are unde-scribed. Aquatic Heteroptera are cosmopolitan exceptin Antarctica, most numerous in the tropics, but withmany distinctly cold adapted genera. Overall speciesrichness is highest in the Neotropical and Orientalregions, which harbor 1289 and 1103 species, respec-tively. In comparison, species richness is significantlylower in the Afrotropical (799 species), Australiasian(654 species), Palearctic (496 species), Nearctic (424species), and Pacific (37 species) regions. AquaticHeteroptera utilize an exceptionally broad range ofhabitats, from marine and intertidal to arctic andhigh alpine, across a global altitudinal range of0–4700m. Species are found in almost every freshwa-ter biotope, plus inland saline habitats, and manyexhibit striking morphological adaptations to theiraquatic environment (Plates II, III), therefore are excel-lent subjects for ecological and biogeographic studies.The term ‘inland waters’ excludes species inhabit-

ing dry terrestrial or marine habitats, but can includemarine species that also inhabit essentially fresh-water. To present a balanced picture of the aquaticHeteroptera of the world, both the entire global faunaand the inland waters component are provided inTable 1.

Heteroptera are hemimetabolous insects, typicallydeveloping via a series of 5 nymphal instars. Thebody consists of 3 distinct parts (although the headand thorax are closely adjoined in Pleidae and Helo-trephidae), with mouthparts specialized for piercingand sucking (except in the Corixidae) (Plate I). Allaquatic families are predaceous (except Corixidae,which are omnivores), with their prey consisting ofany organism that can be subdued by injection of avenom consisting of toxins and proteolytic enzymes.In aquatic systems devoid of large fishes, aquaticHeteroptera often represent the top predators in thetrophic chain; this is particularly true for the largerBelostomatidae and Nepidae.

Diverse stridulatory mechanisms are widespreadin aquatic Heteroptera, occuring in both familiesof Leptopodomorpha, the Gerridae and Veliidae inGerromorpha, and most families of Nepomorpha.

Modern water bug lineages can be traced back byfossil evidence to the Mesozoic, with some, such asBelostomatidae relatives, occuring in the Triassic,180million years ago. Cladistic evidence indicatesthat they are most likely derived from terrestrialancestors. The phylogeny of the Heteroptera as awhole and of the individual infraorders within hasbeen presented in a series of cladograms by Schuh andSlater.

Diversity is highest in first to third order streams(i.e., the smallest streams in a given drainage net-work), and lowest in large rivers and lakes. A highpercentage of tropical endemics are found associatedwith rheocrenes or headwater streamlets, often inproximity to waterfalls or other habitats with highstructural complexity. There are only 19 Holarcticspecies in four families, Saldidae (12), Corixidae (5),Gerridae (1), Veliidae (1).

Biology of Selected Families

Leptopodomorpha

Leptopodidae (ghost bugs)Leptopodids can be separated from saldids by theshort 4-segmented rostrum, deeply punctured dor-sum; male genitalia is symmetrical and female ovipos-itor plate-like. The Leptopodidae are primarily anOld World saxicolous (living on rocks) group,known from warm temperate and tropical regions,

323

cr

ca

pf

pl

cs

vc

ef

slc

m

co

cl

s

p

a

hr

tr

ta

th

765

4

2

f

cx

r

sp

Plate I Morphology, Saldidae: Saldula pallipes, structures

1. Dorsal view2. Ventral view: a, antennae; ca, callus; cl, clavus; cr, collar; cs, claval suture; co, corium; cx, coxae; ef, embolar fracture; f, femur; h,

hemelytra; hr, hypocostal ridge; m, membrane; p, pronotum; pf, pronotal furrow; pl, posterior lobe; r, rostrum; s, scutellum; slc,

sublateral cell; sp, female subgenital plate; t, tibia; ta, tarsi; tr, trochanter; vc, veins of the corium. Adapted from Polhemus JT (1976)

Shore bugs (Hemiptera: Saldidae, etc.). In: Cheng L (ed.). Marine Insects, pp. 225–262. Amsterdam: North Holland & Elsevier.

324 Invertebrates _ Hemiptera (True Bugs)

including Australia and New Guinea. Some generaare mainly or exclusively riparian, on steep rockwalls or boulders or beneath stones, while others arefound far from water such as the monotypic Nearcticgenus Saldolepta. The Old World Patapius spinosus(Figure 1), sometimes found near water, has beenintroduced into North and South America and Japan.All species are predacious, and the few prey records

include psocopterans (bark lice, book lice) and chi-ronomid midges.Leptopodids of the widespread genus Valleriola are

very agile, running rapidly over riparian rock sur-faces, and flying at the slightest disturbance. Theyare very difficult to see because their colorationmatches the rock, hence the name ghost bugs. Mostof the meager knowledge of the biology of these bugswas given by Pericart. The eggs are laid either on thesurface or in cracks of rocks.All of the Old World leptopodids have a stridula-

tory mechanism, except Leotichius, which calls intoquestion its inclusion in the subfamily Leptopodinae.Saldidae (shore bugs). The Saldidae are unique in

having a side-by-side mating/coupling system involv-ing a serrate female ovipositor that fits into a notch(parandria) in the distal male abdomen then capturedby the parameres (genital claspers), plus a male lateralabdominal clamp that grasps a modified region of the

costal wing margin of the female. This allows the pairto jump while still coupled.

The Saldidae is a rather large family distributedworldwide, ranging from the intertidal zone to almost5000m on mountain tops, and from the tropics to thearctic tundra. The greatest diversity is in the temper-ate, boreal and Arctic-alpine zones of the Holarcticregion, where they are a primarily hygrophilous(moisture-loving) and littoral group. They feed pri-marily on Diptera larvae or other small invertebrates,both newly dead or disabled, and on live prey insubsurface soil layers; the latter are located bymeans of chemoreceptor setae on the antennae. Litto-ral saldids swarm around alkaline and saline lakeshores, predating on huge numbers of fly larvae. Spe-cies whose life history is known can overwinter asadults, nymphs or eggs depending on the species andlocal conditions.

Most shore bugs are notably agile, jumping andflying at the slightest disturbance. The exceptionsare the mostly tropical Rupisalda and allied generathat live on vertical rock faces, and retreat to depress-sions in the rock when disturbed.

The largest genus Saldula, with about 150 species,is worldwide, but mainly holarctic and includesgroups that rightly belong in separate genera. InSouth America, most littoral saldids belong to

2

4

5

7 8 9

6

1

3

Plate II Aquatic Heteroptera

1. Notonectidae: Notonecta undulata2. Pleidae: Neoplea striola

3. Nepidae: Ranatra fusca

4. Notonectidae: Buenoa margaretacea5. Belostomatidae: Benacus griseus

6. Belostomatidae: Abedus sp. (Male, with eggs on back)

7. Nepidae: Nepa apiculata

8. Naucoridae: Pelocoris carolinensis9. Belostomatidae: Belostoma flumineum Adapted from Hungerford HB (1920) The Biology and Ecology of Aquatic and Semiaquatic

Hemiptera. Kansas University Science Bulletin 11: 1–328.

Invertebrates _ Hemiptera (True Bugs) 325

Pseudosaldula, most hygropetric species to Rupi-salda. There are about 30 saldid species knownbut undescribed, most of them in Pseudosaldula,Rupisalda and Saldula. Salt-loving Pentacora spe-cies occur both on Nearctic seacoasts and inlandsaline habitats; P. signoreti (Pl. III. 10) is known

from the seashore to alpine salt springs at 3000m.Some Ioscytus species are restricted to alkalinesoils, others prefer peat bogs. Several saldid spe-cies in Hawaii and one in the Marquesas Islandslive in arboreal mosses in mountainous cloudforests.

12 3

45

67

8 9 10

Plate III Semiaquatic Heteroptera

1. Hebridae: Hebrus concinnus

2. Hydrometridae: Hydrometra martini3. Veliidae: Rhagovelia obesa

4. Gerridae: Trepobates pictus

5. Gerridae: Gerris marginatus

6. Mesoveliidae: Mesovelia mulsanti7. Veliidae: Microvelia pulchella

8. Gelastocoridae: Gelastocoris oculatus

9. Ochteridae: Ochterus americans10. Saldidae: Pentacora signoreti

Adapted from Hungerford HB (1920) The Biology and Ecology of Aquatic and Semiaquatic Hemiptera. Kansas University Science

Bulletin 11: 1–328.


Table 1 Aquatic Heteroptera Fauna of Inland Waters Summary

excludes fossils, (x) total genus/species number of aquatic

Heteroptera including species of marine and xeric habitats

Family Genera Species

Leptopodomorpha

Aepophilidae 0 (1) 0 (1)Omaniidae 0 (2) 0 (6)

Leptopodidae 8 (10) 32 (39)

Saldidae 25 (29) 322 (335)Total 33 (42) 354 (381)Gerromorpha

Gerridae 62 (67) 700 (751)

Hebridae 9 (9) 221 (221)Hermatobatidae 0 (1) 0 (9)

Hydrometridae 7 (7) 125 (126)

Macroveliidae 3 (3) 3 (3)

Mesoveliidae 12 (12) 46 (46)Paraphrynoveliidae 1 (1) 2 (2)

Veliidae 56 (60) 896 (962)

Total 149 (161) 1992 (2109)NepomorphaAphelocheiridae 1 (1) 78 (78)

Belostomatidae 9 (9) 160 (160)

Corixidae 32 (32) 419 (419)Gelastocoridae 3 (3) 111 (111)

Helotrephidae 21 (21) 180 (180)

Micronectidae 3 (3) 188 (188)

Naucoridae 37 (37) 391 (391)Nepidae 15 (15) 268 (268)

Notonectidae 11 (11) 400 (400)

Ochteridae 3 (3) 68 (68)

Pleidae 3 (3) 38 (38)Potamocoridae 2 (2) 8 (8)

Total 140 (140) 2309 (2309)

Total 323 (343) 4656 (4799)

Figure 1 Leptopodidae: Patapius spinosus. Froeschner

RC and Pena LEG (1985) First South American record for the

circum-Mediterranean Patapius spinosus (Rossi) (Heteroptera:Leptpodidae). Revista Chilena de Entomologia 12, 223. Original

drawn by Y Sohn, Smithsonian Institution, Washington, D.C.


Gerromorpha

Gerridae (water striders, pond skaters)can be separated from the Veliidae by the head with-out a median impressed line, scutellum hidden, cov-ered by a pronotal lobe, and claws usually insertedpreapically (before apex).The Gerridae (Pl. III. 4, 5), with eight subfamilies,

comprise one of the largest families of the semiaquaticHeteroptera, and occupy a wide variety of habitats,from the open ocean to high mountain rheocrenes.Gerrids of the oriental subfamily Eotrechinae have

well developed claws, preterminal or terminal, thatpermit them to be semiterrestrial (all other gerridshave small preterminal claws). Many of the speciescan move rapidly over vertical rock faces, either wetor dry. In the largest genus, Amemboa, only a fewspecies are commonly found on the surface of quietwaters. Most species rest on shore at the water’s edgeor on wet depressions, where their cryptic colorationessentially hides them unless they move, and thenonly their silvery markings are evident.

The other genera are increasingly adapted towardterrestrial life. The genus Eotrechus has terminalclaws and the species generally live on verticalrock faces, often around waterfalls. One species,E. brevipes Andersen, lives on steep dry rock surfaces,and has been found far from water on a forest trail.

It is now generally accepted that the ecologicalevolution of the Eotrechinae proceeded from waterto land as a secondary adpatation, thus despite thepossession of apical claws, usually considered a prim-itive character, the genus Eotrechus does not repre-sent the most ancestral branch of the Gerridae.

Most Ptilomerinae are Asian, plus one genus inMadagascar. They have two distinct derived charac-ters that immediately separate them from other ger-rids, i.e., they can, and do, readily skate backwards,and when handled exude a compound with a verydistinct and characteristic pungent smell.

Species of the largest genus Ptilomera (Figure 2)generally skate on fast flowing streams, often in thestrongest current where ripples on the water makethem very difficult to detect. There they snatch insectsthat have fallen into the surface film and are beingrapidly carried downstream.

The genus Potamometropsis occupies even fasterwater, sometimes crashing torrents, warranting thevernacular name ‘torrent striders.’

Figure 2 Gerridae: Ptilomera tigrina. [Copyright DA Polhemus].


Rhyacobates imadatei, an inhabitant of large riverson Borneo, skates with great speed and agility in areasof strong current, then rapidly approaches a midstreamboulder, leaps 12–15 cm onto the wet shady surface torest before leaping off to pursue prey once again.The Gerrinae are the best known water striders, as

the genera Aquarius, Gerris and Limnoporus arecommon on ponds and streams throughout Europe,North America and temperate Asia.Gigantometra are the largest water striders, with

bodies up to 35mm in length, and a total leg span of260mm (10þin). These live on modest sized streamsin southern China and north Vietnam.The Subfamily Trepobatinae has more than 130

species in 26 genera distributed mostly in the south-ern hemisphere on fresh and salt water; these smallwater striders have radiated extensively on the islandof New Guinea and nearby archipelagos. There areonly two genera in North America, and none inEurope.Most are weak skaters, however Ciliometra species

often skate on rapidly flowing smooth water.There are only two genera in the Rhagadotarsinae,

Rheumatobates in the New World, and Rhagadotar-sus in the Old World. The females have a well devel-oped ovipositor, unique in the Gerridae.Rheumatobates has species in both marine and

freshwaters; in Florida, four species occupied a singleestuary partitioned according to salinity.In the Halobatinae, the most speciose genus Halo-

bates is mostly marine, including five species on theopen ocean, but has two species on freshwater riversin northern Australia, and one New Guinea speciesthat occurs throughout the length of estuaries withmixohaline (salt plus fresh) to limnetic waters.Cylindrostethinae are large water striders, and

some of the strongest skaters (e.g., Potamobates)belong to this group, which is tropicopolitan.

Charmatometrinae with only three Neotropicalgenera and 11 species, is the smallest subfamily ofGerridae, found on still waters.

Hebridae (Velvet Water Bugs, Sphagnum Bugs)

With micro- and macrohair layer covering bodyexcept the abdomen, short transverse scutellum andadjoining triangular metanotum plus ocelli presentexcept in apterous species.

This family is cosmopolitan and they are oftencharacterized as living on the surface of ponds, how-ever most of the species actually live on the banks, oron steep rock surfaces.

The large genus Hebrus (Pl. III. 1), with more than100 species, has many more tropical species thantemperate, a large number of them undescribed.

The genus Timasius prefers vertical rock surfacesjust above swiftly flowing water. Some species ofHyrcanus are found submerged in the sheetingwater of cascades and waterfalls. The southeastAsian genus Nieseriella lives amongst the stones onthe bottom of swift streams along with elmid beetles,therefore evidently utilizes plastron respiration.

Several completely apterous species are known,one described as Austrohebrus, the others unde-scribed, that taxonomically are very similar to thefamily Paraphrynoveliidae.

Hydrometridae (Marsh Treaders, Water Measurers)

The Hydrometridae (Pl. III. 2) have extremely elongatebodies and legs, allowing them to walk in stilt-likefashion across the surfaces of ponds and streampools. They are characterized by the hidden scutellum,covered by pronotal lobe, claws usually inserted api-cally, and the head distinctly prolonged behind eyes.

This rather large family is cosmopolitan, but mostprevalent in the tropics. The largest genusHydrometrawith about 120 species is cosmopolitan; one species inMadagascar lives on plant stems far from water, butits feeding habits are not known. Five species of anundescribed genus in French Polynesia (Marquesas,Moorea, Tahiti) live in arboreal mosses, and twomonotypic Marquesan genera are found on alpineplants; these constitute one of the primitive clades.The four Heterocleptes species are semiterrestrial inAfrica and Borneo, as is the Amazonian Veliometraschuhi. The neotropical subfamily Limnobatodinaehas only one species, so far taken only at lights.

Macroveliidae (Macroveliid Water Bugs)

In this family, the scutellum not exposed, but covered bypronotal lobe, the claws are usually inserted apically,and the head is not distinctly prolonged behind eyes.

Figure 3 Macroveliidae: Macrovelia hornii. Usinger RL (1956)

Aquatic Hemiptera In Usinger RL (ed.). Aquatic insects ofCalifornia. pp. 182–228. Berkely, CA: University of California

Press With permission.


The Macroveliidae (Figure 3) has only three mono-typic genera that occupy a narrow range of habitats.Macrovelia and Oravelia inhabit springs or seepswith abundant vegetation in western North America,the latter in only one locality in California. Chepuve-lia is found in wet forest litter in southern Chile,usually collected by sifting or Berlese funnels.

Mesoveliidae (Water Treaders, Pondweed Bugs)

Characterized by micro- and macrohair layerrestricted to head and prosternal regions of the thorax,and the scutellum is exposed in macropterous forms.TheMesoveliidae has 12 genera placed in 2 subfami-

lies, that occupy a wide range of both lotic and lentichabitats. The very common and widespreadMesoveliamulsanti (Pl. III. 6) in the New World, and Mesoveliavittigera in the Old World, inhabit still waters withmuch vegetation, where they run rapidly over the sur-face when disturbed, thus the common name pond-weed bugs. But most mesoveliid species are cryptic,living on banks, damp places, mosses, or on stones inthe water, thus are not obvious. Mesoveliids feed onalmost any organism, including ostracods.In the subfamily Madeoveliinae, ocelli are absent,

and the tarsal claws are inserted preapically. Thereare two genera with a few species, Madeovelia fromAfrica, Mesoveloidea from the Neotropics, usuallyfound in lotic habitats, on mossy rock or log surfaces.

In the subfamily Mesoveliinae, ocelli are present inmacropterous forms, reduced or absent in apterousforms, and the tarsal claws are inserted apically. Thelargest genusMesovelia, having 26 species at present,is cosmopolitan.

Phrynovelia, Austrovelia, Mniovelia, and Seychel-lovelia live on rheocrenes or in litter. Cavaticovelialives in lava tubes on Hawaii, and the two species ofSpeovelia live in shallow caves near the seashore inMexico and Japan.

Paraphrynoveliidae

All known specimens are apterous, very similar toapterous Hebridae, except with the usual three tarsalsegments.

This is a very small family, with one genus contain-ing two species, restricted to southern Africa. Thebest known populations inhabit damp mosses onTable Mountain near Capetown, and little is knownabout their feeding or life history.

Veliidae (Small Water Striders, Water Crickets,

Riffle Bugs)

In the Veliidae, the scutellum is not exposed, butcovered by pronotal lobe and the claws are usuallyinserted preapically.

This is the largest family of semiaquatic Hetero-ptera, with six subfamilies that occupy an extremelywide variety of habitats from the intertidal zone tohigh mountain rheocrenes, and from secluded habi-tats to large streams.

Ocelloveliinae, with one genus and two species inSouth Africa, has been variously placed in Mesovelii-dae, Macroveliidae, and Veliidae. They have ocelli,3-segmented tarsi, and pretarsus inserted preapically.

Rhagoveliinae, currently with only one very largecosmopolitan genus Rhagovelia (Pl. III. 3), has morethan 300 species, characterized by the deeply cleftmiddle tarsi with a plumose swimming fan arisingfrom the base of the cleft. These bugs generallyskate on flowing streams, often in the strongest cur-rent, where they snatch insects that have fallen intothe surface film and are being carried downstream.

Orange colored species are almost always foundin shaded parts of streams. The grey coloration ofspecies inhabiting open waters is thought to blockUV rays. There are many undescribed species onMadagascar, and perhaps 50 on New Guinea.

Perittopinae, with a single Asian genus Perittopus,has 11 species found on the quiet parts of streams.The coloration is unusual, red to orange, with blackwings. The subfamily Veliinae contains the largestveliids (10mm). They usually inhabit streams orponds, but also a wide range of habitats, including

Figure 4 Aphelocheiridae: Aphelocheirus philippinensis.

Usinger RL (1937) A new species of Aphelocheirus from Australia(Hemiptera, Naucoridae). The Australian Zoologist 8: 341–342.


foam masses in streams, tree holes, and both arborealand ground living bromeliads.Some are negatively phototropic, hiding in holes

under the banks during the day, emerging to feed atnight.Members of the speciose subfamily Microveliinae

(Pl. III. 7), with 39 genera and 413 species, usually arefound around ponds or streams, but occupy anextremely broad range of habitats including foammasses in streams, and many container habitats suchas treeholes, bamboo internodes, bromeliads andcrabholes. The genera Hebrovelia, Tonkuivelia, andVeliohebria are semiterrestrial. Several genera aremarine, not inland. Microvelia longipes uses ripplecommunication.Several genera exhibit phoresy; in Phoreticovelia,

or Zeus Bugs, with four species in the western Pacific,the tiny males are phoretic on the much larger femalesand feed on secretions from pronotal glands.In Haloveliinae, the most speciose genus Halovelia

is mostly marine intertidal, but other genera, such asEntomovelia and Strongylovelia, have several specieson freshwater rivers in the Malay Archipelago andAsia. In Australasia, species of Xenobates occurthroughout the length of estuaries with mixohaline(salt plus fresh) to limnetic waters.

Nepomorpha

Aphelocheiridae (Benthic Water Bugs)Aphelocheirids (Figure 4) are oval flattened bugs withnon-raptorial fore legs, hind legs fringed with swim-ming hairs, but not oar-like. They are characterized bythe rostrum extending at least one-half length ofmesosternum, antennae long, slender.In all Aphelocheiridae, as in some Naucoridae,

respiration is via a plastron of ultramicroscopichairs that allows them to remain submerged fortheir entire lives in depths up to 10m. They hunt forprey beneath stones in swift running waters, as well asstill waters. Their prey consists of various inverte-brates including molluscs.The single genus Aphelocheirus with 78 species,

restricted to the Old World, is much more prevalentin the tropics.

Belostomatidae (Giant Water Bugs, Electric LightBugs, Toe Biters)All species are flattened and ovoid, with retractilebreathing straps (Pl. II. 5, 9). Most species have pow-erful fore-femora for grasping prey, and middle andhind legs adapted for swimming. The notable excep-tion is the African genus Limnogeton Mayr, in whichall legs are slender and the beak is very long, whichfacilitates feeding on the harmful snails that harbor

schistosomes, the cause of Bilharzia disease or Schis-tosomiasis in humans.

The size ranges from small (9mm) to the largestwater bugs (110mm). They are fierce predatorswith powerful venom, the largest capable of subduingsizable fish, and even a full grown woodpecker.Strongly attracted to light, they are often called elec-tric light bugs.

Unique in the Insecta, female Belostomatinae, andsometimes Lethocerinae, deposit their eggs on thebacks of males (Pl. II. 6).

Until very recently the South American genusHorvathinia was known only from light traps, buthas now been collected from a permanent pond innorthern Argentina.

Corixidae (Water Boatmen)The broad triangular nonsegmented labrum, and lackof a scutellum (except in Diaprepocoris) characterizethe Corixidae (Figure 5). They are mostly omnivores,but some are carniverous. The fore tarsus, usuallyformed as a spoon-shaped pala, scoops bottom oozeas food, but in predacious species is claw-like andraptorial.

The subfamily Diaprepocorinae, with only fourspecies in Diaprepocoris (Figure 6) from Australiaand New Zealand, soon may be raised to familyrank. Both this and Micronectidae are distinguishedby the possession of a large obvious scutellum,

Figure 5 Corixidae: Sigara variabilis. [Copyright PP Tinerella].

Figure 6 Corixidae: Diaprepocoris barycephala. [Copyright

PP Tinerella].


lacking in other corixids, but Diaprepocoris hasocelli, unique in the Corixoidea.

Of the remaining four subfamilies, two are cosmo-politan, one is Neotropical, and one is African. Sev-eral species are used as human food in Mexico, andwidely used as pet food.

Gelastocoridae (Toad Bugs)Gelastocorids have a distinctly toad-like appearance(Pl. III. 8), and hop when disturbed, hence their name.The antennae are short and hidden, the male genitaliaare strongly asymmetrical, the female genitaliaslightly so.

The largest genus Nerthra (Figure 7), with 91species, is cosmopolitan. All species are riparian;however some Nerthra may be found far fromwater, and often burrow. Most Gelastocoris speciesare found in the open and not concealed.

Helotrephidae (BB Bugs)The Helotrephidae, or BB Bugs, are distinguished bythe complete or nearly complete fusion of the headand prothorax into a cephalonotum (Figure 8). Thesecompact, globular bugs usually swim upside down,inhabiting quiet waters of lotic and occasionally len-tic ecosystems.

Helotrephids are restricted to the tropics, and showgreatest diversity in southeast Asia.

Micronectidae (PygmyWater Boatmen) TheMicro-nectidae (Figure 9), formerly a subfamily in Corixidaeand sharing the broad triangular nonsegmentedlabrum, is now considered by several workers to bea separate family, and is treated as such here. Thedistinguishing characters are the small size (<1mm–5mm), exposed scutellum, three segmented antennae,lack of ocelli, eversible palar claws of the males, andstridulation by movement of the male genital capsule.

Figure 7 Gelastocoridae:Nerthra sp. [Copyright DA Polhemus].

Figure 8 Helotrephidae: Ascetotrephes edmundsorum.

Polhemus JT and Polhemus DA (2003). A new genus of

Helotrephidae from peninsular Malaysia and Borneo(Heteroptera: Helotrephidae). Tijdschrift voor Entomologie 146:

209–218. Original drawn by Y Sohn, Smithsonian Institution,

Washington, DC. In the public domain, no copyright.

Figure 9 Micronectidae: Micronecta carbonaria. [CopyrightPP Tinerella].


This is one of the largest groups in the Corixoidea,and more genera and species will be added soonbecause of the interest of several taxonomists.

All species feed in the same way as Corixidae, andare sometimes found in huge numbers, usually wherefish are absent. Most species are known both flight-less and fully capable of flight, and are common inlight traps. The genus Micronecta can be used toassess water quality.

Naucoridae (Creeping Water Bugs, Saucer Bugs)Naucorids (Pl. II. 8) are oval flattened bugs with ashort stout rostrum, and short hidden antennae. Theforelegs are raptorial, and the middle and hind legsmodified for swimming in most species.

Naucorids occupy a wide variety of habitats,ponds, lakes, as well as fast and slow flowing streams.The genera and species are often quite specific as topreferred habitat, with many endemics in warmsprings. They are predacious on small arthropodsand molluscs as far as is known. Some species arewing dimorphic (with two distinct forms); howeverflight has rarely been observed. Eggs are glued onplant stems or pebbles, and nymphs occupy similarhabitats. Some species in the temperate zone hiber-nate, while most inhabiting warmer waters do not.

The family is distributed worldwide, but is muchmore prevalent in the tropics. The numerous NewGuinea naucorids are endemic to that island. Crypho-cricos species utilize plastron respiration, and alsopresumably does Procryphocricos, as they remainpermanently submerged. These live among the stoneson the bottom of swift streams, and their legs andclaws are fitted for crawling rather than swimming.Cryphocricos has been found up to 10m deep.

Cheirochela species live beneath large stones indeep swift water in southeast Asia. Namtokocorilives in holes and crevices of hygropetric rock wallsand waterfall splash zones in southeast Asia; someAmbrysus species and Interocoris mexicanus areoccasionally found in similar habitats in theNeotropics.

Nepidae (Water Scorpions, Water Stick Insects) TheNepidae (Pl. II. 3) are most closely related tothe Belostomatidae, belonging to the same clade.The body is cylindrical or flattened, with a siphon topierce the water surface for air (Figure 10). Theirbodies resemble sticks and leaves, allowing them toremain motionless as sit-and-wait predators alongpond or stream margins, waiting for prey to comewithin reach of their mantid-like forelegs. They arepoor swimmers, but able to propel themselves with

Figure 10 Nepidae: Laccotrephes pfeiferiae. [Copyright JT

Polhemus & DA Polhemus].


jerky leg motions. Static sense organs function to keeptheir proper orientation in the water.Nepid morphology is unusual, for adults have only

one segmented tarsi; all other aquatic Heteropterahave at least two tarsal segments on one or more legs.Adults and nymphs of most New World Ranatra

species possess a stridulatory mechanism, which maybe unique within the aquatic insects.Eggs are often laid in plants or mud banks, but

some Ranatra species have a lanceolate operculum(lid over genital chamber) that facilitates ovipositionin plant stems. Most nepid species have five instars;however the American Nepa apiculata (Pl. II. 7) hasonly four. Death-feigning (playing dead) is commonfor Nepa.An eyeless Nepa is the top predator in a closed

Romanian cave system.

Notonectidae (Backswimmers)Notonectids (Pl. II. 1) are relatively large (5–15mm),with a strongly convex dorsum, large eyes, oar-likehind legs, and they swim upside down, hence theirname. Some species are wing dimorphic, the flightlessforms with reduced flight wings.All species are generalist predators, locating their

prey visually or by surface ripples (Notonecta), feed-ing on amphipods, insects (including mosquito lar-vae), small fishes, and any other small creature theycan catch and subdue. Most species live in the quietparts of streams or in lentic habitats. Martarega aresedentary predators, waiting in schools for prey nearthe surface in quiet parts of streams; when disturbedthey skip over the surface like minnows.Overwintering can occur as eggs or adults or both.

Usually eggs are laid in or on aquatic vegetation, butNotonecta eggs are often found on rocks orsubmerged debris. As far as known, there are fivenymphal instars.

Notonecta are worldwide, but much more speciosein the Holarctic region. The genera Anisops andBuenoa (Pl. II. 4) use haemoglobin to bind or releaseoxygen, allowing individuals to attain neutral buoy-ancy and remain quietly suspended at any depthin the water column, giving them a significant preda-tory advantage over most other aquatic insects. Thesetwo genera are usually geographically separated, inthe Old and New Worlds; however both have nowbeen introduced into Hawaii, where females are diffi-cult to separate.

Ochteridae (Velvety Shore Bugs)Ochterids are saldid-like in appearance, but haveshort, barely visible antennae. The small family Och-teridae (Pl. III. 9) is distributed worldwide, but ismuch more prevalent in the tropics. The largestgenus Ochterus, with 65 species, is cosmopolitan,Ocyochterus is Nearctic, and Megochterus is Austra-lian. Some ochterids occupy muddy or sandy shoresas do the Saldidae, and they largely replace the latterin tropical littoral habitats. Many tropical species arefound on vertical hygropetric (wet rock face) habi-tats, where they may coexist with saldids. Other spe-cies are cryptic, living under the banks of streams.

Eggs are laid singly on plant debris or sand grains.Nymphs cover their back with sand grains as a cam-ouflage. They overwinter as adults or late instarnymphs. All species are predacious on arthropods asfar as is known. A few species are wing dimorphic.

Pleidae (Pygmy Backswimmers)These are small, globular bugs, 1.5–3mm in length,heavily punctured, with a short broad head immobilerelative to their thorax (Pl. II. 2). Not needed Pleidsswim upside down as do the notonectids, but theylack the oar-like hind legs, as all legs are similar.

They frequent vegetated still waters worldwide butare most diverse in the tropics, feeding on mosquitolarvae, ostracods, and other small arthropods. A fewspecies are wing dimorphic.

PotamocoridaeThese bugs (Figure 11) are separated from naucoridsby the short rostrum, just reaching onto the proster-num, and long slender antennae.

This small Neotropical family has two describedgenera, and another undescribed genus from Belize.

Nothing is known of the biology, as almost allspecimens have been collected at lights; howeverone female Potamocoris was collected from a water-fall plunge pool in Colombia.

Figure 11 Potamocoridae: Potamocoris parvus. Hungerford

HB (1941) A remarkable new naucorid water bug (Hemiptera).

Annals of the Entomological Society of America 34: 1–4.


Conservation

Aquatic Heteroptera are hardy and adaptable insects,and based on current information it appears thatmost species are not at risk. There are a few docu-mented cases in Europe, North America, and Japan,

where taxa with particularly circumscribed rangeshave become endangered through loss of habitat.For tropical regions, our documentation of speciesranges and ecologies is so incomplete that no solidconclusions can be drawn, but potential threats existfrom both human alteration of landscape ecologies(such as conversion of rain forests to plantations orcattle pastures) and from ecosystem transformationsdriven by global climate change.

Many species of aquatic Heteroptera are useful interms of global or regional conservation planning forpreservation of freshwater biodiversity, due to thelargely nonoverlapping nature of the broad regionalbiotas, coupled with a high degree of localized ende-mism. Certain species are also effective biologicalcontrols of mosquitos and other pest flies becausethey feed on the immatures, and other species havebeen documented as natural enemies of rice pests.

Glossary

Bucculae – A ventrally directed flange on each sideof the base of the rostrum Labrum – Upper lipPhoresy – One organism carried on the body of alarger organsim, but does not feed on the latter.

Plastron – A physical gill formed by a dense mat ofmichrotrichia or microsculptured chitin on the ven-tral body surface.

Primitive clade – A hypothesized monophyleticgrouping nearest to the hypothetical ancestor.

encyclopedia of inland waters || hemiptera (true bugs)

Documents