c. Envenomization. In recent years, more people have died from the bite or
sting of arthropods than from snakebites. Arthropods Iisted as responsible have been
wasps, bees, ants, caterpillars, spiders, scorpions, and centipedes. The great majority
of deaths have been from wasp and bee stings inflicted on persons who have become
sensitized to these particular venoms.
d. Dermatitis. Dermatitis is a skin irritation that may be caused by ticks, mites,
fleas, bedbugs, and other arthropods. This is usually a local reaction to the presence of
the arthropod, its venom, or secretions. A serious problem that can develop is that of
secondary infection commonly caused by scratching the part of the body bitten or
invaded by the arthropod. Chigger mites are an example of an arthropod that can
cause dermatitis.
e. Myiasis. Myiasis is a condition caused by the invasion of tissues by fly
larvae. An example is the blowfly that lays its eggs in open sores or wounds. In a few
hours or days, depending on temperature or other factors, the eggs hatch and the
larvae invade the tissues of the wound. If the condition goes unnoticed or untreated in
either humans or other animals, it can result in the loss of an Iimb or even death.
f. Allergy. Allergy may be defined as a hypersensitive reaction to arthropod
secretions, excretions, or body parts. It may occur in workers involved in separating
Iight trap catches (see para 3-3e) or anybody working with pulverized insect parts and
scales of butterflies or moths. Allergic reactions may be manifested in various forms;
hives: asthma, hay fever, urticaria, eczema, and so forth. Certain individuals are more
susceptible than others are to these reactions; several factors such as heredity,
predisposition, and previous exposure also may affect the degree of sensitivity.
Section II. CLASS INSECTA
1-5.
MOSQUITOES
a. Mosquitoes belong to the famiIy Culicidae of the order Diptera and constitute
the single most important insect group from the standpoint of both disease transmission
and annoyance. They are distributed throughout the world. Where water is found,
mosquitoes are usually also found. There are over 3,000 described species with a
great variety of habits. Knowledge of mosquito identification and biology is essential for
efficient control.
b. Mosquitoes wilI breed in virtually any collection of water that has been
standing for longer than 5 to 7 days. Those breeding in and around human dwelling
places are called domestic mosquitoes. Different kinds of mosquitoes vary in their
choice of breeding places. Some like sunlit places, whereas others prefer the shade.
Some prefer fresh water to stagnant water; others prefer the brackish water of salt
marshes. Common breeding sites are ponds, pools, slow-moving streams, swamps
and bogs, salt marshes, ditches, tree holes, rock holes, and manufactured water
containers.
MD0170
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