Environmental Engineering Reference
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fattened or cylindrical with long slender legs, the
anterior pair being raptorial with long and stout
femur used mainly for capture of prey. One-
jointed tarsi and absence of ocelli are the charac-
teristic feature of the family. The two long slender
nonretractile caudal fi laments with grooves on
median surface and fi tted together constitute the
respiratory tube. By placing its tip at the surface
fi lm, oxygen in the tracheal system is replen-
ished. Nepids are sluggish in nature and prefer
still water. They are usually found in trash and
mud or remain entangled with aquatic vegetation
in the shallow littoral region of wetlands. Highly
predacious insect species feed mainly on live
insects and their nymph. The prey is captured
with the help of raptorial forelegs. The most
important cosmopolitan genus
Ranatra
occurs
abundantly in this region.
2. Family: Belostomatidae, Leach, 1815
These insects are commonly known as “giant
water bugs” because of their large size (10-
110 mm in length). The body is fl at, oval or
oblong and has brown or dull greenish colour.
The antennae are 4 segmented and concealed in
pockets beneath the head; eyes are prominent.
The strong and thick front legs are raptorial and
used for grasping. The middle and hind legs are
broad, fl at and fringed with swimming hair. The
tarsi are 3 segmented and the ocelli absent. The
most characteristic feature in adult is the pres-
ence of retractile strap-like appendages at the
abdominal apex, which are used to obtain air.
These air straps are homologous with respiratory
siphon of the related family Nepidae, being
derived from the 8th abdominal tergum, each
bearing a basal spiracle. About 150 species of
belostomatids are so far known all over the world.
Adults are large (2 to 2-1/2 in. long), brownish,
somewhat fl attened and broad with the middle
and hind legs fi tted for swimming. The front legs
are fi tted for grasping (praying mantis-like) with
two claws at the tips. The end of the abdomen
bears two short, strap-like appendages for breath-
ing. The head is broad and slightly extended
beyond the eyes. They are very much attracted to
lights and are known as “electric light bugs”.
Sometimes they leave the water and fl y to street
lights some distance away. These bugs feed on
other insects, snails, tadpoles and small fi sh
(sometimes several times their size). They inject
a poisonous fl uid into their prey after capture,
sucking them dry. They occur in ponds and quiet
pools, feigning death when removed from the
water and ejecting a fl uid from the anus. Death is
quick if not able to return to the water. Eggs are
laid in massed rows of 100 or more above the
water on cattails and other plants, hatching 1-2
weeks later. They are vicious biters, infl icting
pain when handled carelessly.
3. Family: Corixidae, Leach, 1815
The members of this family usually called
“water boatmen” are medium to small insects
usually 2-16 mm in length. The family Corixidae
is the largest family of aquatic Hemiptera
consisting of about 500 species, distributed
widely in the world from below sea level to as
high as 4,575 m in Himalaya, from arctic water
beneath ice to hot springs with temperature
around 35 °C (Thirumalai
1989
), in India it is
represented only 35 species belonging to 4 genera.
During present investigation only one species
was recorded. The body is somewhat fl attened
above and its colour is dark greyish with yellow
or black markings. The wing membrane is with-
out veins. The head is triangular with short,
unsegmented labium. The antennae are short and
concealed with 3-4 segments. The front tarsus is
single jointed with scoops-like segment called
“pala” which is characteristic of the family. The
scutellum is concealed and the male abdominal
segments are asymmetrical. A fi le-like plate
called “strigil” is present in tergum VI of male.
Abdominal terga III-IV of nymphs and adults
have metathoracic scent glands opening near the
3rd coxae. Dorsum of the abdomen has an alter-
native dark and transverse band. Adults are about
1/4 in. long, somewhat fl attened, oval, grey-
brown or mottled with the top surface often fi nely
cross lined and the hind legs elongate and oarlike
(fl attened and fringed with hairs) for swimming.
Eyes are black (space between yellow) and legs
and body underparts yellow. They swim rapidly,
usually seen at the bottom in the shallow water of
ponds and lakes, and feed on algae, protozoa,
plankton or dead organic matter on the bottom of
pools and roadside ditches. Some species are
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