Page 15 - Adventures through the World of Entomology

Another of the 30 phyla is the phylum Arthropoda. The members of the phylum Arthropoda have a “gut Another of the 30 phyla is the phylum Arthropoda. The members of the phylum Arthropoda have a “gut
body cavity,” an exoskeleton — a skeleton on the outside of their body, similar to a coat of armor — and body cavity,” an exoskeleton — a skeleton on the outside of their body, similar to a coat of armor — and
jointed appendages. The phylum Arthropoda is, in turn, divided into 9 classes which include such things jointed appendages. The phylum Arthropoda is, in turn, divided into 9 classes which include such things
as shrimp, crabs, spiders, scorpions, millipedes, centipedes, and insects. as shrimp, crabs, spiders, scorpions, millipedes, centipedes, and insects.

Graphics using the Linnaeus System showing five classes of Arthropoda. Graphics using the Linnaeus System showing five classes of Arthropoda.

KINGDOM KINGDOM
ANIMAL ANIMAL

PHYLUM PHYLUM
ARTHROPODA ARTHROPODA

CLASS CLASS CLASS CLASS CLASS CLASS CLASS CLASS CLASS CLASS
Arachnida Crustacea Insecta Chilopoda Diplopoda Arachnida Crustacea Insecta Chilopoda Diplopoda

Spiders Sowbugs Ants Centipedes Millipedes Spiders Sowbugs Ants Centipedes Millipedes
Ticks Pillbugs Beetles Ticks Pillbugs Beetles
Scorpions Shrimp Fleas Scorpions Shrimp Fleas
Mites Lobster Crickets Mites Lobster Crickets
etc... etc... etc... etc... etc... etc...

Many more phyla with many more classes going through hundreds of orders, thousands of families, Many more phyla with many more classes going through hundreds of orders, thousands of families,
tens of thousands of genus and species can be categorized using this method. tens of thousands of genus and species can be categorized using this method.

Spiders, scorpions, millipedes, and centipedes are sometimes thought of by homeowners as insects, Spiders, scorpions, millipedes, and centipedes are sometimes thought of by homeowners as insects,
but they are not. They belong to classes that are different from the class Insecta. By definition, the but they are not. They belong to classes that are different from the class Insecta. By definition, the
members of the class insecta have: (1) a segmented body divided into three parts – head, thorax, and members of the class insecta have: (1) a segmented body divided into three parts – head, thorax, and
abdomen, (2) jointed appendages – three pairs of legs – each pair attached to one of the three segments abdomen, (2) jointed appendages – three pairs of legs – each pair attached to one of the three segments
of the thorax – and a pair of antennae located on their head, and (3) an exoskeleton. Also, many species of the thorax – and a pair of antennae located on their head, and (3) an exoskeleton. Also, many species
have one or two pairs of wings. We now have a definition of an insect. have one or two pairs of wings. We now have a definition of an insect.

ANTENNA ABDOMEN ANTENNA ABDOMEN
HEAD HEAD

THORAX THORAX

LEG LEG

Photo Courtesy of UNVAR Photo Courtesy of UNVAR Photo Courtesy of UNVAR Photo Courtesy of UNVAR
Each of the three parts of the insect has other parts connected or located consistently on or in them. Each of the three parts of the insect has other parts connected or located consistently on or in them.
HEAD: antennae, eyes, mouth; THORAX: legs, wings, spiracles; ABDOMEN: spiracles, cerci, ovipositor HEAD: antennae, eyes, mouth; THORAX: legs, wings, spiracles; ABDOMEN: spiracles, cerci, ovipositor