Environmental Engineering Reference
In-Depth Information
scavenger beetles” are characterized by their
short-clubbed antennae that generally remain
concealed beneath the head and long maxillary
palps resembling antennae like Dytiscidae; they
also make contact with the surface water fi lm
with the anterior edge of their body, but unlike
the former, their hind legs move alternately
while swimming, and they are not very good
swimmers. Adults are good fl iers and some
leave the water and crawl on land. The air sup-
ply is through the tracheal system and spiracles
from subelytral chamber and from silvery fi lm
of air retained on ventral side of the body by
hydrofuge hairs. For the renewal of oxygen sup-
ply, the beetles come to the surface with body
slightly inclined to one side so as to keep the
cleft between head and thorax in contact with
surface fi lm. The surface fi lm is broken by
antennal tip. They feed mainly on detritus, algae
and decaying vegetative matter. Biswas and
Mukhopadhyay (
1995
) provided the latest
account of Hydrophilidae from West Bengal,
wherein 40 species belonging to 19 genera are
dealt. Adults are large about 1-1/2 in. long, hard
bodied and elliptical with triangular yellowish
markings on the abdomen sides. The body top is
smooth and shiny black with a greenish tinge. A
long spinelike keel on the thorax underside
between the legs can be jabbed into the fi ngers
when the beetle is handled carelessly. The
antennae are club shaped and the legs are fl at-
tened for swimming. They are good fl iers and
are very much attracted to lights in large num-
bers in the spring. Beetles are commonly seen
swimming or crawling among the water plants
or on the bottom of shallow pools, feeding
mostly on dead or decaying vegetation. The
hind legs move alternately when swimming.
The larvae are predaceous and cannibalistic.
There are one to two generations per year.
4. Family: Haliplidae
The Haliplidae or crawling water beetles are a
comparatively small group of inconspicuous,
small water-dwelling insects. The family con-
tains fi ve genera and about 200 species are known
worldwide. Adults live among aquatic vegetation
along the edges of ponds, lakes, streams or
creeks. The crawling water beetles are best iden-
tifi ed by the large coxal plates covering the base
of the hind legs and abdomen. Although they are
mainly crawlers, they do have swimming hairs on
their legs and do sometimes swim. Their tarsi
have two claws. They are omnivores found in the
vegetation of pools. They are small beetles with
their size at maturity of about 2-6 mm. Regimbart
(
1882
) recorded the fi rst Indian species
Haliplus
angustifrons
from Bihar. So far seven species are
recorded under the genus
Haliplus
from India.
5. Family: Elmidae
This is a family of small beetles 2-5 mm long.
They have punctured elytra and raised lines on
the thorax. They live in running water. Some
breathe underwater using an air fi lm trapped by
hairs as a physical gill. About 300 species are
known worldwide. Elmids are small beetles, usu-
ally less than 3 mm long, and most are aquatic in
both adult and larval stages. The adults breathe
by means of a hydrofuge ventral plastron and the
larvae with retractile cloacal gills. Adults and lar-
vae inhabit the substratum of creeks and rivers,
feeding on diatoms, encrusting algae detritus or
submerged decaying wood, and they are good
water quality indicators. The riffl e beetles usually
have fi liform antennae that are much longer than
the head. Their tarsi are distinctly fi ve segmented.
They are underwater crawlers and do not swim;
therefore, they have no swimming hairs on their
hind legs. They have 5-6 abdominal segments.
Beetles belonging to the family Elmidae (riffl e
beetles) live in running water. Some breathe
underwater using an air fi lm trapped by hairs as a
physical gill, mostly aquatic in both adult and lar-
val stages. Water beetles, especially Elmidae, are
gaining increasing recognition as indicators of
water quality, water types and endangered habi-
tats (Jach and Matsui
1994
).
Order: Coleoptera
I. Family: Dytiscidae
Subfamily: Hydroporinae
1 .
Hydrovatus confertus
(Sharp)
2 .
Guignotus fl ammulatus
(Sharp)
3 .
Guignotus inconstans
(Reg)
Subfamily: Notorinae
4 .
Canthydrus laetabilis
(Walker)
5 .
Canthydrus morsbachi
(Wehncke)
6 .
Hydrocoptus subvittulus
(Mots)
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