Download giant water - University of Guelph Laboratory Services

PEST DIAGNOSTIC CLINIC
Laboratory Services Division, University of Guelph
95 Stone Rd. West, Guelph, Ontario N1H 8J7
Phone: (519) 767-6299
E-mail: [email protected]
Web: www.guelphlabservices.com
THE GIANT WATERBUG
Lethocerus americanus (Leidy) (Hemiptera: Belostomatidae)
These interesting aquatic insects are also known as electric light
bug, toe biter or fish killer. They have little economic importance in
Ontario, but may be a problem in fish culture operations. These
insects can cause a painful bite and most bites occur in conservation
areas, ponds or other fresh water recreation areas where a swimmer
has accidentally come in contact with the giant water bug. They are
attracted to lights and sometimes can be found scattered on the
ground adjacent to a lamp standard.
DESCRIPTION: Overall length - approx. 5cm (2 in.)
Head: Two large black eyes separated by a very strong "beak" that
is held tightly against the ventral surface of the insect.
Image source:
http://museum.gov.ns.ca/
mnh/nature/nhns/t11/t11-16.pdf
Thorax: Front legs are raptorial and are usually held out in front of
the head. They are used for grasping prey. The front legs are twice
as thick as the other legs and this is a good identification feature of
this insect. The middle and hind legs point towards the back of the insect and their prime
function is for swimming. The wings of the giant water bug are brown and leathery in texture
and are held flat against the abdomen.
Abdomen: The most of the abdomen is covered by the wings, except for two tube-like
appendages at the posterior end. The tubes are the ends of spiracles and enable the insect to
suck air from the water surface and store it underneath the wings for diving.
LIFE CYCLE
During the spring and early summer, eggs are laid near or in water attached to aquatic plants,
stones, leaves or rotting branches. The eggs are a muddy, brownish-grey colour, 4-5mm long,
laid in rows. Usually 100 are found in each group. Depending on the temperature, the eggs
hatch in approximately 2 weeks. The nymphs look very similar to the adults except they are
without wings and are much smaller. A nymph will moult 5 times before becoming an adult.
Both the nymphs and adults feed on aquatic insects, tadpoles and small fish. They will either
chase their victim or pounce on it when it is in range. They first grasp their prey with their
powerful front legs and then begin to suck the body juices of their victim using their large beak.
The majority of this insect's time is spent searching for food on the bottom of the pond. The
adult insect will periodically swim up to the water surface and float at an angle so its posterior
end is just breaking the surface. The insect does this in order to restore the air bubble, which is
kept between the abdomen and wings.
PDCF-087 (Revised 2012-06-25)
During the late fall and winter months, the nymphs and adults burrow into the mud at the bottom
or side of the pond. In order to find new breeding and egg laying sites, the adults will often
leave the pond and fly around until another body of water is found. Sometimes the insect flies
into a swimming pool and is quickly killed by the chlorine. This insect is also attracted to lights.
USEFUL REFERENCES
Borror, D.J. and R.E. White. 1970. A Field Guide to the Insects. Houghton Mifflin Company,
Boston.
Usinger, R.L. 1956. Aquatic Insects of California. University of California Press, Berkley, Los
Angeles, London.
H. Goble/T. Young
PDCF-087 (Revised 2012-06-25)