A SURVEY OF PREDATORY AQUATIC INSECTS

PREDATORY INSECTS OF VARIOUS FISH PONDS

DETRIMENTAL TO POLYCULTURE: A SURVEY

INTRODUCTION

Aquatic insects which occur in various types of fish ponds such as nursery, rearing and

stocking are considered to be harmful for planktivorous fish in general and particularly their

larval stages such as spawn, fry and fingerlings. The fish ponds such as nursery, rearing and

stocking are invariably heavily infested with aquatic insects after maturing particularly during

monsoon period. The destructive role of predatory aquatic insects in different types of fish

ponds are well documented (Distant, 1960; Gorai and Ray Chaudhry, 1962; Tripathi and

Sharaf, 1974). Many predatory aquatic insects not only directly prey upon spawn, fry and

fingerlings of carps but also compete with them for their food organisms (Julka, 1956;

ganguly and Mitra, 1961).The damage by predatory insects has often been mentioned as one

of the major constraints to the aquaculture production (Penak, 1953 and Alikunhi, 1956).

Insects rarely live in extensive bodies of water such as the oceans. Some live on or near the

surface water while other penetrates into deep water. Many obtain oxygen from the air above

the surface (the semi-aquatic species) while some truly aquatic insects obtain their oxygen

from water. There are various degrees of adaptation to the aquatic habitat. They modify

themselves in various ways to obtain food. As a rule, aquatic situations offer an abundance of

food, chiefly in the form of plants. Many of the Chrysomelidae and Lepidoptera feed upon

the portions of the plants that protrude above water. Hydrophilid beetles and many other

species devour the submerged portions of plants. Bellura bores into stem of lilies. Donaica

larvae feed upon roots of aquatic plants. However, predacious Heteroptera-Notonecta, Nepa

and Ranatra attack living insects and even turn upon fish and other small animals.

These aquatic insects are one of the major problems of nursery ponds. These insects not only

affect the carp but a major threat for their survival in the nursery pond. For the survival of

carp spawn, it is essential that the pond is cleared of its insect population immediately before

stocking. Repeated seining of pond with a fine-meshed net before stocking does not eradicate

the predatory insects. Control of insects is done by various insecticides, oils and chemicals.

Effective control of insets is obtained via insecticides. But their disadvantage is that they also

have some harmful effect on carp also.

Movements and type of Aquatic insects

Clingers: Have bodies that are good at maintaining a solid position on firm surfaces in water

and in a current. Lotic-erosional habitat. Physical adaptations: Flat bodies, offers little

resistance to water flow. Sucker-like structures creating a vacuum. Produce a silk that serves

as sticky glue. Ex. water pennies, caddis flies, black flies, snails, flatworms, leeches.

Climbers: Adapted to live on aquatic plants. Long bodies with spindly legs used to move up

and down plant stalks. Often greenish in color. Lentic-littoral and lotic-depositional habitat.

Ex. Damselflies, dragonflies.

Crawlers: Lives on a solid surface, and seeks out protected places among pebbles or rocks.

They move slowly, and use their legs and front claws. They need shelter from the current.

Almost all crawlers are lotic-erosional. Ex. Hellgrammites, stoneflies, mayflies.

Sprawlers: Lives on sand, silt, or clay. Flattened bodies, legs extend out so they can maintain

their bodies on top of the sand and not sink below. These insects lie still and do not move

often. They live in the lentic-littoral, lotic-depositional, and some amount in the lotic-

erosional habitats. Ex. Snails, dragonflies, some caddis flies.

Burrowers: These insects like to dig themselves down into the sand, silt, or clay. Scoop-like

front legs, pointy-heads, long pointed body, special mechanism for obtaining D.O. above

them. Live in lentic-littoral, lentic-profundal, lotic-depositional, and some lotic-erosional. Ex.

Mayflies, midges, aquatic earthworms, dragonflies, some crayfish.

Swimmers: Active movements. Move their entire bodies like a fish would swim. Some have

long tails to push them forward, like oars on a boat. Legs are usually flat. All types of lentic

and lotic habitats. e.g. Minnow mayflies, mosquitoes.

Skaters Surface water movement gently without breaking through the film created by surface

tension. Usually small bodied. Long thin legs. Special hairs on legs and body, with glands at

bases of fine hairs secreting an oily substance to keep hairs from becoming wet. Lentic and

lotic-deposition e.g. Water striders.

Feeding types

Shredders: Chew on pieces of plant material, basic mouthparts, and two mandibles, e.g.

Giant stoneflies.

Collectors: Acquire and ingest small particles. Two kinds of collectors; filters and gatherers.

Gatherers eat food on the bottom, filters create water current for feeding with body

movement, e.g. Aquatic earthworms.

Scrapers: Consume thin layers of algae attached to rocks, etc. Jaws have an angled shape

like a putty knife, e.g. Mayflies, water pennies, snails.

Pierces: Mouthparts with elongated adaptations to pierce and suck prey. Two kinds of

pierces; herbivores, e.g. Water beetles, adult micro-caddis flies and predators, ex. predacious

diving beetle and giant water bug.

Order Hemiptera – Water Bugs

Hemiptera are hemimetabolous exopterygotes. All aquatic Hemiptera belong to the suborder

Heteroptera. There are about 300 species of Hemiptera in North America that are adapted to

living in or on the water (McCafferty, 1981). In contrast with most aquatic insects both the

adult and immature stages are associated with water, and they share the same habitat as well

as having similar body form (Daly, 1998; Lehmkuhl, 1979). Most aquatic Hemiptera are

found in lentic waters, but a few are found in lotic waters (McCafferty, 1981). Several species

are found in brackish, intertidal, and marine habitats (Cheng, 1976; Cheng, 1985; Glausiusz,

1997; McCafferty, 1981). The families Notonectidae, Corixidae, Nepidae, Belostomatidae,

Naucoridae, Gerridae, and Veliidae will be discussed. All aquatic Hemiptera are predators or

scavenger. All aquatic Hemiptera are aeropneustic. Hemipterans have a beak-like mouth that

is either conelike or a more elongated piercing, sucking structure. The abdomen lacks gills,

filaments, and cerci. A few species lack wings (McCafferty, 1981). If handled improperly

these insects can inflict a painful bite. Members of the family Notonectidae are commonly

known as backswimmers. Backswimmers are 5-16 mm long, and there are approximately 30

species found in

North America (McCafferty, 1981). They are found in pond, streams and lake margins, small

pools, and intertidal marshes (Daly, 1998; Kellogg and Kellogg, 1994). As would be expected

by the common name, backswimmer, and the Notonectidae swim on their backs. They have

natatorial, or swimming legs. The middle and hind legs are covered with long hairs, and the

hind legs are oarlike. The front legs are adapted for holding prey (Lehmkuhl, 1979).

Backswimmers trap an air bubble with hairs on the body. This form of respiration is called a

plastron. Some aquatic insects have a plastron that allows oxygen from the water to diffuse

into it, which is termed a physical gill. Notonectidae generally prey on other insects, snails,

and small fish (McCafferty, 1981). The family Corixidae consists of the insects commonly

known as water boatmen. There are over 100 species found in North America (McCafferty,

1981). Adults are 3-11 mm long (Lehmkuhl, 1979; McCafferty, 1981). Water boatmen

resemble backswimmers in many respects, and often inhabit the same types of habitats. Some

are associated with brackish water, intertidal marshes, and salt pools (Cheng, 1976; Daly,

1998; Kellogg and Kellogg, 1994). As previously mentioned the Notonectidae

and Corixidae are similar in several ways including body shape, structure of the middle and

hind legs, and use of a plastron for respiration. Two distinguishing characteristics are that

water boatman is that they do not swim on their backs, and water boatman has a modified

beak (Lehmkuhl, 1979; McCafferty, 1981). The beak is short, blunt, triangular, and not

distinctly segmented. This unique beak design does not restrict to consuming only juices as in

most other Hemiptera (McCafferty, 1981). Water boatmen are herbivore, detritivores,

omnivores, predators, or scavengers depending on the species (Daly, 1998; McCafferty,

1981). Insects that are commonly referred to as water scorpions belong to the family Nepidae.

There are 13 species of water scorpions found in North America (McCafferty, 1981). Water

scorpions are 15-45 mm (excluding the breathing tube) long and are either narrow or elongate

or broad and oval in form (McCafferty, 1981). Nepidae respire through a long caudal

breathing tube, or snorkel. The legs are long and narrow. The fore legs are raptorial (Daly,

1998; Kellogg and Kellogg, 1994; Lehmkuhl, 1979; McCafferty, 1981), while the posterior

legs are adapted for walking among aquatic vegetation and debris where they stalk prey

(Daly, 1998). Water scorpions are poor swimmers (Daly, 1998; McCafferty, 1981), but they

mostly inhabit aquatic vegetation and debris of lentic waters and therefore do not need to be

good swimmers. The group of insects commonly known as the giant water bugs belongs to

the family Belostomatidae. There are approximately 20 species of belostomatids found in

North America (Lehmkuhl, 1979; McCafferty, 1981). These can be some of the largest

aquatic insects and are usually 20-65 mm long (McCafferty, 1981). They are somewhat

flattened and oval in form. Giant water bugs obtain oxygen through a pair of retractile strap-

like appendages that are located at the tip of the abdomen (Lehmkuhl, 1979). The fore legs

are raptorial, and the middle and hind legs are fringed with hairs for swimming. The large

raptorial fore legs allow belostomatids to attack prey that can be up to 20 time larger in size

(Kellogg and Kellogg, 1994). Males of the genera Belostoma and Abedus carry eggs on their

backs (females glue them there) until they hatch. Common names other than giant water bugs

include fish killers, electric light bugs, and toe biters. The name fish killer refers to the

voraciousness of some species that will attack small fishes and other small animals such as

ducklings (McCafferty, 1981). The name electric light bug refers to the tendency of

dispersing adults to be attracted to lights at night (McCafferty, 1981). The name toe biter

refers to the fact that some species are known bit the toes of waders and swimmers

(McCafferty, 1981). The family Naucoridae contains the insects called creeping water bugs.

There are approximately 20 species found in North America (McCafferty, 1981). Adults are

6- 15 mm long (McCafferty, 1981). Creeping water bugs superficially resemble giant water

bugs, but they are more rounded and streamlined in the dorsal aspect (Daly, 1998), lack strap-

like respiratory appendages on abdomen (Lehmkuhl, 1979), and lack veins in the

membranous area of the hemiptera (McCafferty, 1981). These insects respire through a gas

bubble or in some species by a plastron (Daly, 1998). Naucorids are the only Hemiptera that

have a physical gill type plastron, which enables them to remain permanently submerged

(Daly, 1998). The fore legs are raptorial, and the middle and hind legs may or may not have

swimming hairs. The raptorial fore legs are used to capture prey that consists mainly of small

arthropods (Daly, 1998). Naucorids are found mostly in quiet water, and some species are

commonly found in hot springs and desert pools (Lehmkuhl, 1979; McCafferty, 1981). The

superfamily Gerroidea contains the families Gerridae, Veliidae, Hydrometridae, Hebridae,

Mesoveliidae, and Macroveliidae. These are not truly aquatic insects, but they are found

closely associated with the shores and surfaces of aquatic habitats. The families

Hydrometridae, Hebridae, and Macroveliidae are more terrestrial species, while the families

Gerridae, Veliidae, and Mesoveliidae are more aquatic and are usually found on the surfaces

of water (Daly, 1998; McCafferty, 1981). They are commonly called water striders and water

treaders. Members of all three of these families contain species that are found in association

with intertidal or marine environments (Cheng, 1976). The genera Halobates of the family

Gerridae contain 5-7 species worldwide that inhabit the open oceans (Cheng, 1976; Cheng,

1985; Glausiusz, 1997). The family Gerridae will be considered in greater detail. There are

approximately 60 species of Gerridae found in North America (Lehmkuhl, 1979). Gerrids are

usually 3-20 mm long, and some species may lack wings (McCafferty, 1981). As these are

not submerged species no special adaptations for respiration are needed, and they simple

breathe through spiracles. Some species, especially those that inhabit rough waters, do have

hairs that cover their body to form an air bubble to float them back to the surface if they are

submerged (Cheng, 1976; Cheng, 1985; McCafferty, 1981). The gerrids have long legs and

some species have hair on their legs, which enable them to walk or skate on the surface of the

water. These insects feed on insect that fall in the water or capture prey through the surface of

the water.

Order Megaloptera – Fishflies, Dobsonflies, and Alderflies

Megaloptera are holometabolous endopterygotes. Only the larval stage of these insects are

aquatic (Daly, 1998; McCafferty, 1981), and all species are aquatic in this stage (Daly, 1998).

There are approximately 300 species worldwide that are distributed mostly in temperate

regions (Daly, 1998); of these only about 50 species are found in North America

(McCafferty, 1981). These insects are most abundant in cool, well oxygenated streams (Daly,

1998), and are commonly found under stones. The larvae, which are commonly called

hellgrammites, are 10-90 mm long (McCafferty, 1981). Larvae have well developed chewing

mouthparts including large mandibles, filamentous antennae, and poorly developed eyes.

Thoracic legs are present. Each abdominal segment contains filaments for respiration

underwater, and the filaments of some species have tufts of gills at the base to increase

respiration (Daly, 1998; McCafferty, 1981). Some species also have spiracles on a pair of

elongate breathing tubes at the end of the abdomen, which are raised above the surface of the

water for respiration (McCafferty, 1981). The abdomen ends with two elongate medial

appendages or prolegs. Larvae of the Megaloptera are all predaceous, and will attack

anything that is small enough to subdue with their large mandibles (Daly, 1998).

Order Neuroptera – Spongillaflies

Only one family of the order Neuroptera has an aquatic stage in its life cycle. This family is

the Sisyridae or spongillaflies. Spongillaflies are holometabolous and are also

endopterygotes. There are two genera and six species of spongillaflies found in North

America (McCafferty, 1981). The larvae are the only stage that is aquatic. The larvae are

small, soft-bodied, and bristled in form, and they are usually 3-8 mm long (McCafferty,

1981). Larvae have thoracic legs that each end in a single claw. Respiration is cutaneous, and

takes place over the general body surface (McCafferty, 1981). The mouthparts are modified

into a needlelike structure that is used for feeding on the cells and juices of freshwater

sponges (Lehmkuhl, 1979; McCafferty, 1981).

Order Coleoptera – Water Beetles

There are over 1000 aquatic or semi aquatic species of beetles found in North America

(McCafferty, 1981). Beetles are also holometabolous endopterygotes. Members of the

families Gyrinidae, Haliplidae, Dytiscidae, Hydrophilidae, Noteridae, Hydraenidae,

Dryopidae, Elmidae, Psephenidae, and Amphizoidae are considered to be aquatic (Epler,

1996; Lehmkuhl, 1979; McCafferty, 1981). In some of these families only the larvae are

aquatic while in others both the larvae and adults are aquatic. The families Gyrinidae,

Dytiscidae, and Hydrophilidae, which are the most commonly encountered water beetles, will

be discussed further. The family Gyrinidae consists of the whirligig beetles. There are over 50

species found in North America (McCafferty, 1981). Both the larvae and adults are aquatic.

Whirligig beetles are found in a variety of lentic and lotic habitats, especially ponds and

streams (McCafferty, 1981). The larvae are elongate and up to 30 mm long (McCafferty,

1981). The abdomen has lateral filaments for respiration, and terminates in four small hooks

(Lehmkuhl, 1979; McCafferty, 1981). The larvae are predaceous. Larvae leave the water to

pupate, and make a pupal cell out of mud or plant material (Lehmkuhl, 1979). The adults are

oval and somewhat flattened. They are 3-15 mm long (McCafferty, 1981). Adult are found on

the surface of the water, but they can dive if necessary. When they dive an air bubble is

trapped under the elytra for respiration underwater. The fore legs are relatively long and

adapted for grasping prey, and the middle and hind legs are short. They swim in circular,

gyrating, and whirling manner, which is why they are called whirligig beetles (Daly, 1998;

Lehmkuhl, 1979). The eyes are divided for simultaneous aerial and submarine vision, and it is

sometimes said that they have four eyes. Adults often form large groups that may contain

several species (Daly, 1998; Lehmkuhl, 1979; McCafferty, 1981). They have club shaped

antennae that are sensitive to surface film disturbance, which allow them to avoid one another

while swimming and to locate insect that fall in the water on which they feed (Daly, 1998).

Adult Whirligig beetles will also feed on floating debris and small aquatic organisms. Some

species release defensive secretions when they are disturbed or handled (McCafferty, 1981).

The predaceous diving beetles make up the family Dytiscidae. There are over 400 species

found in North America (McCafferty, 1981). Both the larvae and adults are aquatic, and can

be found in nearly all aquatic habitats. The larvae are 5-70 mm long (McCafferty, 1981).

They have slender legs and mandibles that are grooved or hollow for suctorial feeding (Daly,

1998; McCafferty, 1981). The abdomen of some species has lateral filaments. The abdomen

is usually strongly tapered at the end and lack terminal hooks (McCafferty, 1981). Fringes of

hair on various parts of the body aid in swimming (Lehmkuhl, 1979). A few species can

obtain oxygen through lateral filaments, but most species must come to the surface to respire.

The voraciousness of the larvae has earned them the common name of water tiger. Pupation

occurs on shore above the water line (Lehmkuhl, 1979). The adults are oval in shape, and are

1-40 mm long (McCafferty, 1981). Adults, like the larvae, are predatory. The middle and

hind legs are covered with hairs for swimming. Air is trapped under the elytra for respiration

underwater. There are several characters that distinguish the Dytiscidae from the

Hydrophilidae. These include breaking the surface with the tip of the abdomen, having

filiform antennae, and moving the hind legs in unison for swimming (Lehmkuhl, 1979;

McCafferty, 1981). The Hydrophilidae are commonly known as water scavenger beetles.

There are approximately 200 species found in North America (McCafferty, 1981). Both the

adults and the larvae are aquatic, and are found in nearly all aquatic habitats. The larvae are

4-60 mm long (McCafferty, 1981). The abdomen may or may not possess lateral filaments

which may aid in respiration, but most species must surface for air. The mandibles are

toothed rather than grooved or hollow as in Dytiscidae. Most larvae are predaceous, but a few

feed on algae (McCafferty, 1981). Pupation occurs in damp soil on the shore (Lehmkuhl,

1979). Adults are 1-40 mm long (McCafferty, 1981). They are oval in shape and superficially

resemble predaceous diving beetles, but there are several characters that are used to separate

the two groups. Water scavenger beetles have clubbed antennae rather than filiform as in the

predaceous diving beetles. The Dytiscidae surface with the tip of the abdomen, while the

Hydrophilidae surface with head/antennae first. The dytiscids move their hind legs in unison

for swimming, and the hydrophilids move the hind legs alternately and crawl more than they

swim (Lehmkuhl, 1979; McCafferty, 1981). Adults must surface for air, and an air bubble is

trapped under the elytra. The adults are scavenger, detritivores, and predatory depending on

the species.

Order Lepidoptera – Aquatic Caterpillars

There are approximately 150 aquatic or semi aquatic Lepidoptera found in North America

(McCafferty, 1981). Lepidoptera are holometabolous endopterygotes. This order contains the

butterflies and moths. The families Cosmopterygidae, Nepticulidae, and Noctuidae contain

species that are considered to be semiaquatic (McCafferty, 1981). Nearly all of the truly

aquatic species are found in the Subfamily Nymphulinae of the family Pyralidae (Lehmkuhl,

1979; McCafferty, 1981). The subfamilies Crambinae and Schoenobiinae have some species

that are considered to be aquatic. These caterpillars are stem burrowers in aquatic rushes or

grasses (Lehmkuhl, 1979). The aquatic larvae of Nymphulinae have been divided to two

types: the plant feeders (Nymphulini) and the rock feeders (Argyractini) (Lehmkuhl, 1979).

The Nymphulini contains 10 genera and 23 species. These caterpillars build cases or tubes of

leaves, have short mandibles, and usually lack gills (Lehmkuhl, 1979). The Argyractini

contains 4 genera and 20 species. These species usually live in silk galleries on rock, have

long mandibles, usually have long lateral gills, and graze on diatoms and algae in lakes and

streams (Lehmkuhl, 1979). Many aquatic Lepidoptera larvae also pupate underwater

(McCafferty, 1981).

Diptera – Midges, Mosquitoes, Aquatic Gnats and Flies

There are over 3,500 species of aquatic or semiaquatic Diptera in 20-30 families (Daly, 1998;

McCafferty, 1981). Dipterans are holometabolous endopterygotes. Larvae and some pupae

are considered to be aquatic. The family Chironomidae has more aquatic species that any of

the other orders of aquatic insects (McCafferty, 1981). The larvae are 1-100 mm long

(McCafferty, 1981). They are usually elongate and maggotlike. The larvae of aquatic Diptera

can be found in all aquatic habitats. Feeding methods include filter feeding, scraping and

grazing, scavenging, and being predatory (McCafferty, 1981). The larvae are often active

swimmers with side to side wiggling movements of the body. Some larvae float on the

surface, and others remain on the bottom during the day but come to the surface at night with

migration through the water column may be aided by using a special tracheal bladder as a

hydrostatic organ (McCafferty, 1981). Aquatic pupae may be active or quiescent

(McCafferty, 1981). Two of the most common families, the Chironomidae and the Culicidae,

will be considered in greater detail. The Chironomidae, or midges, are usually the most

abundant macroinvertebrate group, both in numbers of species and individuals, in freshwater

aquatic habitats (Epler, 1995). There are over 100 genera and perhaps as many as 2,000

species in North America (McCafferty, 1981). Midge larvae are usually 2-20 mm long

(McCafferty, 1981). They are slender and usually cylindrical and slightly curved. The body

has one pair of prothoracic legs and one pair of terminal prolegs (Kellogg and Kellogg, 1994;

McCafferty, 1981). Many species have larvae that are bright red due to hemoglobin in their

blood. This allows them to respire in water with low oxygen content, and it gives them the

common name of bloodworm (Daly, 1998; McCafferty, 1981). Feeding types include

carnivores, herbivores, case builders, net spinners, and free-living form (Lehmkuhl, 1979). A

few species are phorectic (ride on) on mayflies and stoneflies (Lehmkuhl, 1979). The remains

and fecal pellets of midge larvae may form organic ooze on the bottom of some aquatic

habitats (Kellogg and Kellogg, 1994; McCafferty, 1981). Some species can live in highly

polluted water, while others need cool clear water. There are over 50 species of midges in 12

genera that are found in marine waters, but only a few are found in the open ocean (Cheng,

1976). The midges Pontomyia sp. and Chironomus oceanicus (Packard) have been found in

30 or more meters of water in marine environments (Daly, 1998). One species of midge

larvae was found in over 1,300 m of water in Lake Baikal of Russia (Daly, 1998). The pupae

maylive within cylindrical or conical cocoons or be free-swimming (McCafferty, 1981). The

family Culicidae consists of the mosquitoes. There are approximately 150 species of

mosquitoes found in North America (McCafferty, 1981). Both the larvae and pupae are

aquatic. The larvae are found in almost all lentic habitats, including many that are only

temporary. Several species are found in intertidal areas (Cheng, 1976; McCafferty, 1981).

They have a swollen thoracic area and have no prolegs, which usually make the larvae easy to

recognize from those of other families (Lehmkuhl, 1979; McCafferty, 1981). The larvae

breathe through a sclerotized siphon (respiratory tube or snorkel). A few species have a

modified respiratory siphon, which they use to piercethe stems of aquatic plants for air

(Lehmkuhl, 1979; McCafferty, 1981). Most mosquito larvae feed on floating or suspended

microorganisms and detritus with sweeping motions of their mouth brushes (McCafferty,

1981). Larvae are often called “wrigglers.” The pupae fused head and thoracic area that are

greatly enlarged, which is distinctive of mosquitoes (McCafferty, 1981). The pupae respire

through thoracic respiratory horns (McCafferty, 1981). The pupae are commonly called

“tumblers.”

Order Collembola – Springtails

The order Collembola contains organisms commonly known as springtails. These are not true

insects, but they are closely related to the insects. They belong to the class Parainsecta. Over

50 species have been reported from various freshwater habitats in North America, but only

10-15 species are regularly associated with the surface of freshwater (McCafferty, 1981).

These species are found in the family Isotomidae, Poduridae, and Smithuridae (McCafferty,

1981). The families Onychiuridae, Hypogastruridae, Neanuridae, Isotomidae, and Actaletidae

contain species that are associated with marine habitats in different parts of the world (Cheng,

1976). Springtails are ametabolous and entognathous. They are usually less than 3 mm long

(McCafferty, 1981). Springtails have one pair of antennae and three pairs of legs. They may

or may not have eyes. They lack wings, wing pads, and cerci (Daly, 1998; McCafferty, 1981).

The furculum/furca (spring) and retinaculum (holds spring in place) allow these organisms to

jump up to 0.2 m through the air, hence the name springtail (Daly, 1998; Lehmkuhl, 1979;

McCafferty, 1981). They feed on algae, fungi, spores, lichens, living and dead plant material,

or dead animals (Lehmkuhl, 1979). Little is known of the special adaptations of apterygotes,

including Collembola, to aquatic environments. They superficially resemble nonaquatic

species (Cheng, 1976).

MATERIALS AND METHODS

COLLECTION OF PREDATORY AQUATIC INSECTS

SAMPLING LOCATIONS

Aquatic insects can be found in nearly any type of aquatic environment including lakes,

streams, springs, wetlands, puddles, and tree holes. The predatory aquatic insects were

collected from those habitats where fish are known to occur, but efforts were made to collect

mainly from fish farms in the northern and central states of India. A survey was made for

studying the species compositions and distribution of aquatic insect fauna. Within a site

sampling was also carried out from different habitats. For example in streams, there may be

riffles, pools, over hanging terrestrial vegetation, aquatic vegetation, leaf packs, and fine

sediment. Habitats that are more heterogeneous will have the greater diversity. In general, the

most diverse habitats are midsized streams flowing through forested regions with alternating

riffle and pool habitats. Insects were collected from various water bodies including fish

ponds.

PRESERVING SPECIMENS

The safest fluids to use are ethanol or isopropyl alcohol for the preservation of sample.

However, isopropyl, absolute alcohol and 5 percent formaldehyde solution were used for the

preservation of collected predatory aquatic insects.

SAMPLING TECHNIQUES

The below mentioned gazettes were used to collect the predatory aquatic insects from their

habitats especially from fish farms:

Dip net (or aquarium net or kitchen

sieve) Forceps

Turkey baster

Light colored pan

Vials with alcohol

Waders or hip boots

Thermometer

Field notebook

Field bag for equipment

Camera

GPS unit

Hand Collection: Aquatic insects were collected with the help of a pair of forceps and a vial

of alcohol. When removed from the water, many insects will crawl from the substrate so they

were placed in a white pan.

Dip Netting: A dip net was found to be particularly effective because sample was collected

from a variety of locations. A dip net can be used in riffles by holding the net downstream

and disturbing the substrate with your hands or feet so that the insects are dislodged and

washed downstream into the net. A dip net is also useful in pools or edge habitats where the

net can be scooped through or under the substrate while being careful not to collect too much

material. This is effective in areas where there is overhanging terrestrial vegetation or

submerged tree roots.

Collecting Adults: Most aquatic insects have terrestrial or aerial adults and so different

technique was used to collect this life stage. At the family level, many aquatic insects are

more difficult to identify as adults. However, many adults can be more reliably identified to

the genus or species level so they may be important for obtaining better taxonomic resolution

in studies. Many adults aquatic insects are attracted to lights so we can collect them at porch

lights since both non-aquatic and aquatic insects are attracted to lights therefore proper

precautions and little adjustment was made to catch insects that are aquatic like insects were

collected near water bodies and light waste accordingly. The easiest way was to use an

aspirator Most aquatic insect adults are not active during the day and are often resting on

vegetation near the water body (although in the cooler months, a greater percentage of adults

are active during the day when it is warmer). Adults were collected using an aerial insect net

and sweeping the vegetation along the edge of a water body and carefully picking specimens

into a vial.

Rearing: Many immature cannot be identified to the species or even genus level without

associated material (i.e., pupae and/or adults). Rearing was done by collecting live mature

late instar larvae or pupae and maintaining them in vials (one organism per vial). Different

insects have different requirements so specific techniques may be required to successfully

rear insects. Some species can be reared in small vials with a small amount of water and a

cotton stopper. Others can be more difficult and will require food, current, or specific

temperatures. Vials were checked frequently for emergence or mortality. Once emergence or

death has occurred, preservative and a label was added to the vial.

LABELING OF SAMPLES

The labels were placed into specimen vials, and care was taken that they can be read when

the vial is held by the cap. Locality labels should be placed so that they are facing out and the

determination label should be facing in. It also helps if the labels are wide enough so that

they curl around the edge of the vial rather than float around with the specimen.

The collected insects were brought to the laboratory for their identification using manuals and

further investigations.

Figure 1: Sample label placement

OBSERVATIONS AND DISCUSSION

It was observed that the depth of the water affects the aquatic insects directly or indirectly.

The insects were seldom found in greater depth. Mostly insects were collected from the

surface and upper part of the water bodies. The insects were found to be more abundant in

comparatively shallow water bodies. The size and shape of water bodies also determine the

abundance of insect life. The abundance of aquatic insects was found to be proportional to

the length of the water bodies because the plants grow more rapidly in shallow water along

the edge.

They do not comprise a systematic group but are scattered through a large number of insect

orders. Out of total insects only 5% are reported to be aquatic belonging to 11 orders of class

Insecta, and out of which the aquatic insects belonging to orders Coleoptera, Hemiptera and

Odonata are considered to be detrimental to polyculture. The freshwater bodies such as lakes,

stream and ponds sustain the greatest population of aquatic insects. The common insect

predators identified from nursery, rearing and stocking ponds were Damsefly, Dragonfly,

Cybister confuseus, Sternolophus ruptpee Gyrinus (Family Gyrinidae), Dineutus corixa

(Family Corixidae), Belostoma indicum (Family Belostomatidae), Notonecta (Family

Notonectidae), Laccotrephes griseus, Anisops bouvier, Ranatra indicum, Hydrophilus

(Family Hydrophilidae), Nepa (Family Nepidae), Micronepta, Agraptocorixa, Macromia,

Libellula (Family Labellulidae), Sphaerodema, Diplonychus and Dytiscus ( Dytiscidae)

Nursery ponds designed to rear spawn of major carps were found to be invariably populated

with large number aquatic insects over greater part of year and especially during and after

rains. Their destructive role in carp nurseries has been described by Khan and Hussain

(1947), Pakrasi (1953), Alikunhi et al. (1955), Alikunhi (1957), Chaudhuri (1960), Ganguli

and Mitra (1961), Gorai and Ray Chaudhuri (1961) and Julka (1965 and 1969). Apart from

preying directly upon spawn and fry of the carp, they also compete with them for their food.

Among Coleoptera members of the families Dytiscidae, Hydrophilidae and Gyrinidae prey

upon fish spawn. Dytiscids, known as predaceous diving beetles, are carnivorous both in

adult and larval stages. They feed on all kinds of aquatic metazoans, larger species commonly

attacking small fish, tadpoles and even dragonfly nymphs (Pennak, 1953). Among

Hemiptera, species belonging to the families Notonectdae (back swimmers), Belostomatidae

(giant water bugs) and Nepidae (water scorpians) cause heavy loss of carp spawn. Back

swimmers abound and start attacking and eating carp as soon as latter are released in ponds.

The back swimmers are known row attack carp spawn small fish, tadpoles and even small

frogs (Distant, 1906). Back swimmers are reported to be capable of killing even 10 to 13 mm

long carp fry. Water bugs are highly predaceous and feed on frogs and fishes.

Predatory aquatic insects multiply rapidly during preparation of pond for stocking of fry and

fingerling and have been found to take heavy toll of fry as soon as the latter are released in

the pond (Penak, 1953; Khan and Hussain, 1947; Ganguly and Mitra, 1961; Gorai and Ray

Chaudhary, 1962; Distant, 1960; Tripathi and Sharaf, 1947). Anisops spp. and its larvae

known to appear in swarms in manured ponds during rainy season and kills up to half inch

(12.7mm) fry, while Laccotrephes spp. and Ranatra spp. can even kill larger fry. Dragonfly

nymphs are highly predatory on carps spawn.

It was observed that some caddis flies prefer clear streams with sandy bottom; other frequent

ponds where vegetables and other sticky materials are abundant. Certain dragon fly and May

fly burrow in the mud. Stone and plants are often essential for the attachment of eggs or

larvae. Accumulation of rich vegetable debris is necessary for the saprophagous species. The

plants provide the insects with hiding places, materials for cocoons, place to lay eggs,

anchorage, food and oxygen. Aquatic insects lay their eggs outside of water bodies but close

to the water. Some species lay their eggs in plants or drop them into the water where they

may fall to the bottom or float freely. Many insects live in the water only as larvae or as

naiads. Insects rarely populate in the water: the Trichoptera and certain Diptera are notable

exceptions. Few adults are stricktly aquatic, although the Gyrinidae, Ditiscidae,

Hydrophilidae, certain Heteroptera and other insects live on the water or dive below its

surface. The species of the genus Pontomyia (Chironomidae) are truly aquatic for they live

completely submerged. Among the truly aquatic insects, the Diptera are considered to be

most outstanding. The larvae of Stratiomyiidae, Chironomidae, cluceidae, Ephydridae and

tabanidae are most numerous. The aquatic insects avoid competition with their overcrowded

terrestrial neighbors. They obtain certain protection for sudden changes in temperature and

avoid numerous parasitic and predacious enemies but acquire new enemies such as frogs,

certain fish and other aquatic predacious animals. The water striders feed largely upon spawn,

fry and aquatic insects that fall upon the surface of water. The predacious Heteroptera:

Notonecta, Nepa, and Ranatara directly attack the spawn, fry, fingerlings and living insects

and even turn up on the fish. The plankton serve as food as food for numerous species of

aquatic insects and compete for the food of juvenile and adult stages of planktivorous species

of fish. Aquatic insects are modified in various ways to obtain food, for example prehensile

front legs. These are well developed in Nepa and Ranatara. The naiads of the Odonata have a

strong lower lip which is an efficient organ for seizing and holding its prey. The net-spining

Trichoptera construct minute silken nets which are placed in the streams to collect

microorganisms. The larvae of the black flies have rake like appendages which sweep in

quantities of diatoms and other microscopic organisms.

More than half of the insect orders have aquatic or semi-aquatic species. The Thysanura,

Collembola, Dicellura, Zoraptera, embiidina and dermaptera are semi-aquatic in nature i.e.,

they live in moist situations, in rotten wood, in decayed live or soil. The Collembola, Podura

aquatic lives on the surface of stagnant ponds, over which they may leap about in great

number. The Ephewmerida, Odonata, Plecoptera and Trichoptera are aquatic in nature. The

immature forms live in the water and breadth by means of tracheal gills. The Neuroptera,

Heteroptera, homoptera, Lepidoptera, Coleoptera, Diptera and Hymenoptera are only partly

aquatic. The immature forms of some are aquatic others are semi-aquatic.

Order Ephemeroptera - Mayflies

Ephemeroptera are exopterygotes and hemimetabolous. The mayflies are all aquatic as naiads

(Daly, 1998). This order gets its name from the mayfly’s ephemeral nature. The naiads may

live for up to a year underwater, but the adults usually live only for a day and at most a few

day. Mayflies are the only insects to molt after reaching the winged form. This stage is called

the subimago. There are over 600 species of mayflies in North America (Lehmkuhl, 1979).

The naiads are usually 3-20 mm long (excluding tails), however a few species may reach 30

mm or more (McCafferty, 1981). The naiads have large compound eyes, short multiarticulate

antennae, and mandibulated mouthparts. The abdomen usually ends with three elongate tails,

which consist of two cerci and a caudal filament. Each leg ends with a claw for clinging to

the substrate in lotic water. Most mayfly naiads have seven pairs of gills on the abdomen for

absorbing oxygen from the water. This number of gills is one way to differentiate mayflies

from other types of naiads (Kellogg and Kellogg, 1994). Most naiads feed on live and

decaying vegetation and detritus. A few species are carnivorous (McCafferty, 1981;

Lehmkuhl, 1979). Mayfly naiads are found in almost all natural and many artificial aquatic

habitats as long as they have sufficient dissolved oxygen (4-10 ppm) (Kellogg and Kellogg,

1994; McCafferty, 1981; Lehmkuhl, 1979). However, the greatest diversity and abundance is

found in streams and rivers. Naiads have a wide range of form including burrowers, filter

feeders, swimmers, clingers, and sprawlers (Lehmkuhl, 1979). Mayflies are common and

important food source for trout. It is for this reason that the mayfly serves as the basis for the

sport and technique of fly fishing and flies tying (McCafferty, 1981).

Order Plecoptera – Stoneflies

Stoneflies are exopterygotes and hemimetabolous. Nearly all Plecoptera naiads are aquatic

(Daly, 1998). There are approximately 500 species of stoneflies found in North America

(McCafferty, 1981). Stonefly naiads are 5-35 mm long. They are found primarily in cold lotic

water, and some are found in cold lakes with lots of wave action. The naiads relatively long

antennae and two long cerci. They closely resemble adults except that they do not have fully

developed wings. Respiration is through single gills found under the legs or through the skin

(Kellogg and Kellogg, 1994; McCafferty, 1981). The legs end in small hooks (2 claws) for

grasping the substrate. The bodies tend to be flattened which allow the naiads to crawl under

stones, hence the name stonefly (Kellogg and Kellogg, 1994; McCafferty, 1981). North

American stoneflies were previously divided into the suborders Filipalpia and Setipalpia, but

this division has been shown to be based on differences that do not always hold. They are

now divided into:

Systellognatha, which have mouthparts adapted for grasping and handling prey and are

primarily carnivorous, and Euholognatha, which have mouthparts adapted to feeding on

detritus, leaf litter, and algae (Pescador, 2000; McCafferty, 1981). The prey of Systellognatha

are small macroinvertebrates.

Order Odonata – Dragonflies and Damselflies

The Odonata are hemimetabolous exopterygotes. Nearly all Odonata naiads are aquatic

(Daly, 1998). The order Odonata contains two suborders: Anisoptera, the dragonflies, and

Zygoptera, the damselflies. There are approximately 450 species in North America

(McCafferty, 1981). All Odonata are predatory in both the immature andadult forms (Daly,

1998; Lehmkuhl, 1979). Naiads are 10-60 mm long (McCafferty, 1981). Odonata naiads are

found in most freshwater habitats, but are most common in ponds, marshes, lake margins, and

shallow areas of streams (McCafferty, 1981). Both the dragonfly and damselfly naiads have a

characteristic feeding method. The labium is hinged in two places and ends with a pair of

spiked jaws or grasping pincers. When not in use the labium is held under the head. It is

extended (shot out) to grasp prey, which includes mollusks, other insects, crustaceans,

worms, and small fish. Both damselfly and dragonfly naiads are usually brown and green to

camouflage them from predators and for ambushing prey (Kellogg and Kellogg, 1994).

Dragonfly naiads have gills located inside the abdomen. Water that is drawn into the

abdomen for the gills can also be forced out to propel the naiad through the water. The

abdomen of dragonfly naiads has five anal appendages: a pair of dorso lateral cerci, a pair of

paraprocts, and an epiproct (Richardson). Dragonfly naiads can be divided into three main

groups: Claspers, sprawlers and burrowers.

Claspers or climbers are usually found among aquatic vegetation where they stalk prey or lie

in ambush for prey to pass.

Sprawlers are usually long legged and are sluggish movers. These forms are ambush

predators that will often accumulate silt on their bodies from remaining motionless.

Burrowers lie beneath the mud, silt, or sand to ambush prey. The eyes and the tip of the

abdomen remain above the surface so they can see prey and respire while the rest of the body

is buried.

Dragonfly naiads tend to have a wide and oval or wide and elongate abdomen, while

damselfly naiads have a narrow body (Kellogg and Kellogg, 1994). Damselfly naiads do not

have gills in their abdomen, but instead have three gills at the end of the abdomen that have a

tripod formation.

Order Trichoptera – Caddisflies

The caddisflies make up the order Trichoptera. Over 1,200 species are found in North

America (McCafferty, 1981). Trichoptera are holometabolous endopterygotes. The larval and

pupal stages of caddisflies are aquatic. They are found in almost all aquatic habitats, but they

are not very tolerant of pollution (Lehmkuhl, 1979). Limnephilus affinis (Curtis) are found in

saltmarsh pools off the coasts of Britain, and Philanisus plebeius (Walker) is found in rock

pools on the coasts of New Zealand and Australia (Cheng, 1976). This group is closely

related to the Lepidoptera, but the adults have hairs on their wings rather than scales as in

Lepidoptera. The scientific name Trichoptera means hair wing, and the common name

“caddis” means case bearer (McCafferty, 1981). The larvae generally consist of two types:

eruciform (cruciform) and campodeiform (Daly, 1998; Lehmkuhl, 1979). Both types of

larvae are elongate and are 2-40 mm long (McCafferty, 1981). They have small, simple eyes

and reduced antennae. Most respiration is cutaneous, but some species may have abdominal

gills (Kellogg and Kellogg, 1994; McCafferty, 1981). Eruciform larvae build cases out of

various types of materials. The anal prolegs are fused and end in a claw for holding the arvae

in the case (Daly, 1998; Lehmkuhl, 1979). Case building forms are often scavengers or

grazers (Daly, 1998). Campodeiform larvae are usually free-living or spin silken nets, and in

these form the anal pro-legs are not fused (Lehmkuhl, 1979).

Most of these forms are predatory (Daly, 1998). There are many intermediate larval forms

(Daly, 1998). Pupation is almost entirely aquatic (McCafferty, 1981), and occurs in the larval

case or in retreat where a pupal case is built (Daly, 1998).

Table 1: Some of the important aquatic insects and their classification

INSECT CLASSIFICATION IMAGE

Eretes sticticus Family Dytiscidae

Subfamily Dytiscinae

Genus Eretes

Species sticticus

Cybister Family Dytiscidae

tripunctatus Subfamily Dytiscinae

Genus Cybister

Species tripunctatus

Nepa cinerea Suborder Heteroptera

Subfamily Nepidae

Genus Nepa

Species cinerea

Ranatra Suborder Heteroptera

chinensis Subfamily Nepidae

Genus Ranatra

Species chinensis

Ranatra fusca Suborder Heteroptera

Subfamily Nepidae

Genus Ranatra

Species fusca

Lethocerus Suborder Heteroptera

americanus Family Belostomatidae

Genus Lethocerus

Species americanus

Gerris remigis Suborder Heteroptera

Family Gerridae

Genus Gerris

Species regmis

May fly Superorder Ephemeropteroidea

Order Ephemeroptera

Dragon fly Order Odanta

Family Libellulidae

Genus Sympetrum

Species flaveolum