AQUA-ENTO
Written by Sajida Sana Waqar-B.Sc
(Hons) Agri.Entomology
Insects have colonized streams, ponds, and lakes multiple times. Aquatic insects are key players in freshwater ecological communities. Aquatic insects represent a fascinating adaptive radiation of arthropods into freshwater environments. These insects often metamorphose into terrestrial adult, or into an adult that inhabits a different part of the aquatic environment than the immature form.
Ephemeroptera
refers to short adult life of insects. These are delicate and slender insects,
most of the species live only for a few hour or day. The habitat of nymph is
fresh running water of ponds and streams; adult is short lived flying insect.
Mouthparts
are chewing and vestigial; antennae are short and setaceous or styliform.
Fore wings are large and triangular; hindwings greatly reduced, or even absent.
Abdomen ends in very long and many segmented two or three long caudal
filaments. The median caudal filament may or may not be present. When present
it is like cerci. Sub imaginal molting
(the fresh adults shed their wings from their body) in winged sub adults present.
The nymphs are called naiads as
these are aquatic, distinguished by seven pairs of gills along the abdomen.
Families
included are: Ephemeridae (Ephemera sp.), Ephemerellidae (Ephemerella sp.), Baetidae (Baetis sp.), Heptageniidae, and Caenidae
(Caenis sp.).
Damselflies.
Characteristics:
Odonata refers to the mandibles,
which are provided with strong teeth in these insects. These are aquatic as
nymph and can be found in fresh water streams, ponds, and rivers. As adults
they are winged and are successful and important predators.Anisoptera is the sub order of dragonflies and Zygoptera is of damselflies.
These insects have
chewing mouthparts and are predaceous in both nymph and adult stages. Their
labium is greatly modified into spoon shaped or prehensile organ or a mask for catching prey, brown and green
bodies tend to provide camouflage and allow nymph to blend with aquatic habitat
of ponds and pond bottoms; antennae are very short and setaceous, compound eyes are very large. Wings are equal in
damselflies and sub equal in dragonflies and are greatly veined, with node and pterostigma. Legs form
a basket below head for catching and eating prey during flight and trochanter is two segmented. Abdomen is
thin and long, secondary male genitalia are present on lower side of 2nd
abdominal segment.
Families
of Anisoptera: Cordulegasteridae (Cordulegaster sp.), Gomphidae (Anarmogomphos sp.), Aeshnidae (Anex sp.), and Libellulidae (Pantala sp.).
Families
of
Zygoptera: Agrionidae (Agrion sp.), Coenagrionidae (Coenagrion sp.), Lestidae (Lestes sp.), and Chlorocyphidae.
Characteristics:
Plecoptera refers to
the anal lobe of hind wings, which are folded fan like at rest. The habitat of
nymph is cold lakes or fast moving streams; adult is the flying insect and
found resting upon stones and tree trunks near the margins of streams and lakes
in the mountainous areas.
These have chewing type
of mouthparts but vestigial; antennae long and setaceous. Hind wings are larger than fore wings and with well
developed foldable anal lobes. Abdomen ends into two long cerci. Nymphs are aquatic, without leaf like gills on abdomen and
with two long caudal filaments.
Families
included are: Perlidae (Perla sp.), Leptoperlidae (Leptoperla sp.), Capniidae (Capnia sp.), and Nemouridae (Nemoura sp.).
Order:
Hemiptera (true bugs)
Characteristics:
Hemiptera refers to the
front wings in which the basal half is thickened and the apical half is
membranous. Its members are found in terrestrial, aquatic, and ectoparasite
habitats. Both nymph and adult lives in ponds, slow moving streams and
intertidal marshes.
These have piercing-sucking types of mouthparts,
with labium modified into sucking proboscis; antennae generally filiform and long. Fore wings are e
modified into hemelytra, with basal
half is thickened and apical half is membranous, hind wings are membranous
throughout and folded under fore wings. These insects have various legs
modification for swimming.
This order further
classified into two suborders:
Cryptocerata (aquatic bugs) and Gymnocerata
(terrestrial bugs).
Cryptocerata
included
the following families:-
Order:
Coleoptera (beetles and weevils)
Characteristics:
Coleoptera refers to
the front wings which act as protective sheath for hind wings, which are folded
under them. Their habitat is slow moving streams, decaying organic matter,
aquatic and semi-aquatic habitats.
These have chewing type
of mouthparts; but in weevils (also known as snout beetles) head is drawn
forward to form elongated snout with the mouthparts at the end; antennae are
varied types. Forewings are hard, thickened elytra meeting in a straight line on back and hind wings are
membranous.
Families
of
Coleoptera including aquatic insects are:
Family:
Dytiscidae
(True water beetle)
Characteristics:
Trichoptera refers to
the dense hair on the wings of most of these insects. The habitat of larvae is
streams and ponds; adult are the land dwelling flies.
These are moth like
insects with chewing type of mouthparts; with long setaceous antennae and no scales on body. Wings are membranous,
hairy, occasionally bear scales and held roof like over the abdomen at rest.
Many Caddisfly larvae can be recognized by soft bodies which are covered by
tube like cases that the larvae build from twigs, leaves, grasses and pebbles.
Some larvae do not build cases where the current is not so strong such as
ponds. They have characteristic motion known as the “Caddisfly Dance”, of wiggling back and forth and up and down. Claspers are well developed at the end
of abdomen.
Families
included are: Hydrophilidae (Hydroptila),
Limnephilidae (rice pests).
Order:
Diptera (True flies, midges, mosquitoes and gnats)
Characteristics:
Diptera refers to the
presence of a pair of front wings in these insects. Their larvae are found in
ponds, lakes, marshes, slow moving streams and some species have adapted to
fast moving streams; adult are flying insects.
These have sponging, or piercing-sucking, lacerating type, cutting- sponging, or rasping and lapping type; antennae are of varied type. These insects have
one pair of membranous wings, the hind pair greatly reduced to knobbed halteres.
Families
of
Diptera including aquatic insects are:
These all organisms are
an important component of aquatic food webs because they break down and process
organic matter and provide food for invertebrates and vertebrates. The species
found in a stream or pond reflect the ecological condition of the aquatic environment
some species occur mostly in well aerated ,rushing streams, others favor low oxygen,
high nutrient environment. Thus, aquatic insects may be used to identify the
water quality of a river or stream.
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