Bugs, Lice, and Fleas
by Dwight Bowman
The word “arthropod” means jointed body.
The most numerous organisms on earth, so in some respects, the
exoskeleton has been more successful than the backbone.
ortunately only a few are truly parasitic on humans.
Fortunately, only a few are truly parasitic on humans.
Primitive arthropods are suggested to have a form that consists of a
body composed of a series of segments where each segment had a
pair of jointed appendages, one on each side; down the center of
the body extended the tube representing the digestive tract.
The exoskeleton, that part which gives them that distinctive “crunch” if
you ever happen to crush one, covers the outside of the body and is
composed of chitin.
To grow or to change their internal and external morphology (the
process of metamorphosis), arthropods must change the external
cuticle that covers their body.
This they do through a process of laying down a new cuticle in a
process called molting, and then, the old cuticle is shed or ecdysed.
The body is composed of hollow spaces with a gut, heart (an open
circulatory system), and gills or tracheae for supplying air.
Four major groups of Arthopods:
The Trilobites comprise a group known only from fossils.
The Crustacea compose the group that includes the well
known shrimp, lobster, crab, and crayfish, along with the
less well known copepods.
The Cheliceriformes include the horseshoe crabs and the
arachnids (the spiders, scorpions, mites, and ticks).
The Uniramia include the Myriapods (millipedes),
Chilopods (Centipedes), and the Insects (Hexapods).
There are some obvious differences in the morphology
f insects and arachnids
of insects and arachnids.
Adult insects have 6 legs, adult arachnids have 8 legs.
Adult insects have three major body divisions (head,
thorax, and abdomen); adult arachnids have two basic
body divisions (cephalothorax and abdomen).
BUGS - HEMIPTERA
The order Hemiptera (Heteroptera to some authors) form the group of bugs
Majority are predacious or feed on plant juices
True bugs tend to be relatively large in size and have a narrow neck that
connects the rather thin head with large eyes to the thorax which has six
well developed legs
Characterized by a hinged
that is folded under the head and
thorax at rest but which is held such that it protrudes from the front of the
insect when it is feeding by piercing the veins of a host or when sucking out
body fluid from a plant or its prey
The wings of the bugs tend to be covered on the anterior half with a leathery
cuticle only apparent in the transparent posterior wing portion
Development is via simple metamorphosis which five
feed in a fashion similar to their adult counterparts
he two important groups in medicine are the
The two important groups in medicine are the
Kissing bugs and the