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he Daily News, Friday, October 6,1995
Storm brings increase in insects
Hurricane Marilyn brought
destruction to the islands' man-
made environment and increased
the numbers of certain species of
insects due to changes in the
islands' ecosystems.
Such insects as mosquitoes have
increased, as have flies and ants. In
the tropics, insects are a major link
in the food chains starting with the
pollination of flowers in tropical
rain forests.
Many insect species are a source
of nutrients for other organisms,
including parasitic and predatory
arthropods. The distribution of tree
species in a tropical forest is clearly
a major selective force in the devel-
opment and maintenance of bird
species diversity in a tropical envi-
ronment
Although certain insects have
increased in number due to the
storm, predators and prey are at
work creating a balance in the
ecosystems. However, one particu-
lar insect most people fear is spi-
ders.
The question is, are spiders
insects? Most people I come in con-
tact with believe so. Spiders are not
insects, but major predators of
insects.
Like insects, spiders have joint-
ed legs and a hard outer skeleton.
The major difference is spiders
have four pair of legs, not three,
with a body divided into only two
regions thorax and abdomen.
Olasee
Davis
Our
Bmirnment
Spiders have no wings even though
some manage to "fly" by "balloon-
ing" on a strand of silk carried by
wind currents. Spiders have no
antennae, but have jaws, which are
called fangs.
Dr. Walter I. Knausenberger, an
entomologist, said, "... the most fas-
cinating and characteristic thing
about spiders is their habit of spin-
ning and weaving silk. This habit
has four functions: to snare or cap-
ture prey as food; to form tubes or
tents for protection; to form egg
sacs for protection of eggs and
newly hatched young; and for loco-
motion."
According to Knausenberger
there are more than 15O species of
spiders in the Virgin Islands. St.
John alone has about 100 species.
The ecological role of spiders is
that of a predator. They kill and
consume a wide variety of insects
from mosquitoes and mites to other
soft-bodied invertebrates. Spiders
kill their prey by biting with their
fangs and injecting poisonous sali-
va.
As predators, spiders are benefi-
cial in keeping insect populations
down. Many of their prey are
insects that damage agricultural
crops or are domestic pests like
mosquitoes.
All spiders are poisonous, but
the fear of spiders is unwarranted
because only a few are dangerous to
human. Of those spiders that do
bite, most produce nothing more
harmful than a minor itch.
Tarantulas and jumping spiders
often are mistaken for poisonous
species. These spiders are usually
large, hairy and formidable, but
their bite is less harmful than a bee
sting. Some people, however, are
extremely allergic to spider venom
and react severely to any spider
bite.
Nonetheless, one spider in the
Virgin Islands is potentially danger-
ous, and people should at least be
aware of its presence. The black
widow spider (Latrodecus mactans)
lives in a web spun in such dark
areas as hollow trees, rock crevices,
abandoned vehicles and covers of
seldom-used buildings.
The male is about -inch long
and all black except for several red
stripes on the side of its abdomen.
The immature female is similarly
colored.
Mature females never attack
unless seriously provoked. They
possess a neurotoxic bite, which
V See SPIDERS, page 27
SPIDERS CONTINUED FROM PAGE 26
Black widows are cannibals
soon after young are born
causes severe pain in the stomach,
muscles and soles of the feet as well
as sweating. The bite sometimes
causes death.
The -inch-long adult female is
mostly shiny black, except for a red
or rare yellow square or hourglass-
shaped mark on the underside of
her spherical abdomen.
The egg sacs are about a half-
inch long and oval. They hold 25 to
900 or more eggs, which undergo
an incubation period of about 20
days. After the spiderlings emerge,
they usually stay near the egg sac
for a few days.
During this time, cannibalism is
prevalent. Eventually, the surviving
spiderlings disperse by means of
small silk threads. When they are
grown, they establish themselves in
some protected place and construct
loosely woven webs.
Our local brown widow spider
with the red hour glass pattern on
the bottom of the abdomen also can
give a serious bite. However, the
most conspicuous spider by far in
the Virgin Islands is the golden silk
spider. They are active in daytime,
and their webs of golden silk
threads span up to 4 to 5 feet across
guts in the rain forest areas and
wooded paths.
With the storm, many insects
became prevalent. Believe me, it is
only natural. If anyone has prob-
lems with spiders, contact UVI
Cooperative Extension Service on
St. Croix at 692-4080 or 778-9491.
Olasee Davis, who holds a mas-
ter of science degree in range man-
agement and forestry ecology, is a
St. Croix ecologist, activist and
writer.
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