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Classification of Bugs
A guide to the Classes & Orders of insects and other arthropods. |
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The Insecta (insects) are a Class of the large animal Phylum
called ARTHROPODA (arthropods) - a name that refers to the jointed limbs. The
other major Classes of living arthropods (i.e. animals related to insects) include the
Crustacea (crabs, lobsters, shrimps, barnacles, woodlice, etc.), the Myriapoda
(millipedes, centipedes, etc.) and the Arachnida (scorpions, king crabs, spiders,
mites, ticks, etc.). In addition there are several minor Classes, the Onychophora
(velvet worms), Tardigrada (water bears), Pentastomida (tongue worms)
and Pycnogonida (sea spiders), all of which contain somewhat aberrant living forms of
uncertain affinities to the any of the preceding groups, and finally a Class of extinct
arthropods, the Trilobita (trilobites), known only from their fossil remains. All
these animals are characterised by a tough outer body-shell or exoskeleton, with flexible
joints between the skeletal plates to allow the animal to move.
<<< GO STRAIGHT TO A CLASS OF ARTHROPODS >>>
The main external body features which distinguish each of the four major Classes of living
arthropods, Crustacea, Myriapoda, Arachnida and Insecta, are shown below (with those that separate
the insects from all other groups highlighted in red). |
CLASS |
MAIN BODY REGIONS |
PAIRS OF LEGS |
PAIRS OF ANTENNAE |
WINGS |
CRUSTACEA |
two - cephalothorax* and abdomen (some with head and trunk) |
five or more |
two |
absent |
MYRIAPODA |
two - head and trunk |
many - one or two per trunk segment |
one |
absent |
ARACHNIDA |
two - cephalothorax* and abdomen |
four |
none (though palps may resemble antennae or legs) |
absent |
INSECTA |
three - head, thorax and abdomen |
three |
one |
usually present (but many wingless forms) |
*cephalothorax = fused head and thorax |
Each of the Classes of arthropods, including the insects, are split
into a number of smaller groups, which reflect progressively more
detailed structural similarities between the group members. These
smaller groups follow a strict hierarchy. The major class divisions in
descending order of size are called Subclass, Order, Suborder, Family,
Subfamily and Genus. A Genus is the smallest group of any real importance
in the naming of individual species, although in some classifications
generic groups may be further split into Subgenera. The scientific name
of a species includes, first, the Genus to which it belongs and, second,
its specific name, e.g. the European Violet Ground Beetle is called
Carabus violaceus, meaning the species violaceus in the
genus Carabus (by convention, generic and specific names are
always printed in italics; the generic name spelt with a capital letter
and the specific name with a small letter). The full classification of
this insect would be as follows: |
PHYLUM: CLASS: SUBCLASS:
ORDER: SUBORDER: FAMILY: SUBFAMILY:
GENUS: SPECIES: |
Arthropoda Insecta Pterygota
Coleoptera Adephaga Carabidae Carabinae
Carabus Carabus violaceus L. |
arthropod insect winged insect
beetle carnivorous beetle ground beetle -
- violet ground beetle |
The name of the author who first describes a species, or a recognised
abbreviation of the author's name, is sometimes quoted after the specific
name of the animal, in this case L. = Linnaeus (the Swedish naturalist
who firmly established the binomial system for naming animals and plants
in 1753, and who published the first descriptive account of this
particular beetle).
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Class Crustacea
Excluding one or two very small groups of shrimps, the crustaceans are
split into 9 main Orders, as listed below. They nearly all live in water
and range from minute planktonic shrimp-like creatures, such as water fleas,
to the large, more familiar, crabs and lobsters. Some members of the Isopoda
are the only forms that have really invaded the land and most of these are
largely confined to damp places. Follow the available links for further
details. |
ORDER |
COMMON NAME |
1. Branchiopoda |
Water Fleas (Daphnia), Fairy, Brine,
Tadpole and Clam Shrimps |
2. Copepoda |
Water Fleas (Cyclops), Fish Lice,
Gill Maggots and Anchor Worms |
3. Ostracoda |
Seed Shrimps |
4. Cirrepedia |
Barnacles |
5. Stomatopoda |
Mantis Shrimps |
6. Mysidacea |
Opossum Shrimps |
7. Decapoda |
Shrimps, Prawns, Lobsters, Crayfish and Crabs |
8. Amphipoda |
Freshwater Shrimps (Gammarus) and Sand Hoppers |
9. Isopoda |
Sea Slaters, Water Slaters, Water Lice and Hog Lice |
Isopoda: Oniscoidea (part) |
Woodlice |
|
Class Myriapoda
There are four groups of centipede-like creatures known collectively
as myriapods. These are listed here as Orders of the Class Myriapoda, but in many arthropod
classifications they are given the status of separate Classes. |
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Class Arachnida
The arachnids are usually split into 8 main Orders, as listed below.
Follow the available links to see examples of some of these groups. |
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Class Insecta
The insects are generally sub-divided into 29 Orders. These are
listed below with links to pages describing general characteristics,
recognition features and examples of each Order. You can also follow
the link at the bottom of this page for a simply
identification key to most of these Orders. |
ORDER |
COMMON NAME |
SUBCLASSES & FEATURES |
1. Thysanura |
Bristletails |
APTERYGOTA
These are wingless insects and their
body structure suggests that they have never had wings during their
evolutionary history. Young stages resemble the adults - little or
no metamorphosis. |
2. Diplura |
Two-pronged Bristletails |
3. Protura |
- |
4. Collembola |
Springtails |
5. Ephemeroptera |
Mayflies |
PTERYGOTA Division EXOPTERYGOTA
These are winged insects, although some
have lost their wings during the course of evolution.When present, the wings
develop externally and there is no marked change (metamorphosis) during the life
cycle. The young stages, called nymphs, resemble the adults except in size and
in lacking fully-developed wings - simply metamorphosis. |
6. Odonata |
Dragonflies |
7. Plecoptera |
Stoneflies |
8. Grylloblattodea |
- |
9. Orthoptera |
Crickets, Grasshoppers
and Locusts |
10. Phasmida |
Stick and
Leaf Insects |
11. Dermaptera |
Earwigs |
12. Embioptera |
Web-spinners |
13. Dictyoptera |
Cockroaches and Mantids |
14. Isoptera |
Termites |
15. Zoraptera |
- |
16. Psocoptera |
Psocids or Booklice |
17. Mallophaga |
Biting Lice |
18. Siphunculata (= Anoplura) |
Sucking Lice |
19. Hemiptera |
True Bugs |
20. Thysanoptera |
Thrips |
21. Neuroptera |
Alder Flies, Snake Flies
and Lacewings |
PTERYGOTA Division ENDOPTERYGOTA
These are winged insects, although some
have lost their wings during the course of evolution. When present, the wings
develop internally (i.e. inside the body of the immature insect) and there is
a marked change (metamorphosis) during the life cycle. The young stages are
very different from the adults and are called larvae. The change from larva
to adult takes place during a non-feeding stage called the pupa
(or chrysalis) - complex metamorphosis. |
22. Coleoptera |
Beetles |
23. Strepsiptera |
Stylopids |
24. Mecoptera |
Scorpion Flies |
25. Siphonaptera |
Fleas |
26. Diptera |
True Flies |
27. Lepidoptera |
Butterflies and Moths |
28. Trichoptera |
Caddis Flies |
29. Hymenoptera |
Bees, Wasps and Ants |
The first priority when trying to identify an
unknown insect is to determine its correct Order. This can be done for
many common insects with the aid of a hand-lens and a moderately simple
key.
 (click icon for
the identification key to insect orders) |
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