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HEMIPTERA, Belostomatidae -- <Images>
& <Juveniles> Description & Statistics
These giant water
bugs are cosmopolitan in temperate and tropical areas. Some species reach 80 mm in length. Important morphological characters include
flattened legs; hind tarsi with two apical claws; fore legs adapted for
grasping prey, the femora enlarged and the tibiae curved; ocelli absent;
antennae shorter than the head, inserted beneath the eyes. All of the
Belostomatidae are predaceous. They
are entirely aquatic as nymphs and pass much time under water as adults. Adults of some species are active fliers
and are frequently attracted to lights.
Females of some species lay their eggs on the back of the male, which
carries them about until they hatch.
Belostomatidae feed on a variety of pond life, including insects, and
in the case of larger species, small vertebrates, e.g., fish and
tadpoles. Sometimes they are harmful
in pond cultures of small fish. They
may also inflict a painful bite to humans.
The family has not been used directly in biological control, although
their predatory activity on mosquitoes may contribute to natural control of
the latter (Cummings 1933, Usinger 1963). Behavior
& Ecology
This is a family of insects in the order Hemiptera, known as giant
water bugs or colloquially as toe-biters, electric-light bugs and Alligator
Ticks (in Florida). They are the largest insects in the order Hemiptera, and
occur worldwide, with most of the species in North America, South America and
East Asia. They are typically encountered in freshwater streams and ponds.
Most species are relatively large (2 cm or more) with some of the
largest, such as Lethocerus, exceeding 12 cm, and nearly reaching
the dimensions (length and mass) of some of the larger beetles in the world.
Giant water bugs are a popular food in Thailand. Bugs of the family Belostomatidae
are fierce predators which stalk, capture and feed on aquatic crustaceans,
fish and amphibians. They often lie motionless at the bottom of a body of
water, attached to various objects, where they wait for prey to come near.
They then strike, injecting a powerful digestive saliva with their mandible,
and sucking out the liquefied remains. Their bite is considered one of the
most painful that can be inflicted by any insect (the Schmidt Sting Pain Index
excludes insects other than Hymenoptera); the longer the bug is allowed to
inject its saliva, the worse the resulting bite, and as the saliva liquefies
muscle tissue, it can in rare instances do permanent damage. Adults cannot
breathe under water, and must surface periodically for air.[1] Occasionally when encountered by a larger
predator, such as a human, they have been known to "play dead" and
emit a fluid from their anus.[1] Due to
this they are assumed dead by humans only to later "come alive" with
painful results.
Belostomatids show paternal care and the eggs of many species are laid
on the male's wings and carried until they hatch. The male cannot mate during
this period. The males invest considerable time and energy in reproduction
and females take the role of actively finding males to mate. This role
reversal matches the predictions of R. L. Trivers' parental investment
theory.
In some areas belostomatids are considered a delicacy, and can be
found for sale in markets. They are often collected for this purpose using
large floating traps on ponds, set with black lights to attract the bugs.
Adults fly at night, like many aquatic insects, and are attracted to lights
during the breeding season. Reproduction
Males attract the females doing a series of periodic movements near
water surface generating ripples in the water known as display pumping. An
accompanying low frequency acoustical signal has been observed in at least
one species of Belostomatinae. Before a female begins ovipositing the
eggs, she mates with the male. Then a series of intercalated matings and
ovipositions occur, females ovipositing 1-4 eggs in each ovipositing bout. An
egg batch can have more than 100 eggs so a couple may copulate more than 30 times
before female oviposits all the egg batch. This increases male confidence of
paternity, a condition thought necessary for the origin of paternal care.
There are two substrates of oviposition, females of species pertaining to the
ancestral subfamily (Lethocerinae) oviposit on emergent vegetation. On the
other hand, Belostomatinae females oviposit on the males' dorsum. The male
will raise the eggs exposing them to air periodically to discourage the
growth of fungus and maintain the viability of the eggs, or conduct a series
of movements below the water known as brood pumping that increases the amount
of oxygen diffusion. The eggs will hatch in approximately three weeks but
their hatching time will decrease as temperature rises. References: Please refer to <biology.ref.htm>, [Additional references
may be found at: MELVYL
Library] Cummings, C.
1933. Bull. Univ. Kansas
34: 197-219. Usinger, R. L.
1963. Aquatic Insects of
California. Univ. Calif. Press,
Berkeley. p. 203-06. |