Arthropod Groups

David J. Shetlar, Ph.D.The “BugDoc”

The Ohio State University, OARDC & OSU Extension

Columbus, OH

© October, 2004, D.J. Shetlar, all rights reserved

What is Entomology?

The study of insects (and their near relatives).

What are insects (and near relatives)?

Insects and their relatives areARTHROPODS.

Review of Zoological Nomenclature(classifying & naming)

Taxonomic Categories

PhylumClass

OrderFamily

GenusGenus & species

Review of Zoological Nomenclature

Taxonomic Categories

Kingdom - AnimalaePhylum - Arthropoda

Class - Hexapoda (=Insecta)Order - Coleoptera

Family - ScarabaeidaeGenus - Popillia

Genus & species -Popillia japonica Newman

Characteristics of the PhylumArthropoda

The segmented bodies are arranged into regions, called tagmata (e.g., head, thorax, abdomen).

The paired appendages (e.g., legs, antennae) are jointed.

They posses a chitinous exoskeletion that must be shed during growth.

They have bilateral symmetry.

The nervous system is ventral (belly) and the circulatory system is open and dorsal (back).

What are some other Animal Phyla?

Protozoa - single-celled animals.

Platyhelminthes - flatworms, tapeworms

Nematoda - roundworms

Mollusca - clams, snails & slugs, squids

Echinodermata - starfish, sea urchins

Annelida - segmented worms (earthworms)

Chordata - fish, amphibians, reptiles, birds, mammals

Arthropod Groups (taxa)

The arthropods are divided into two large groups that exist today:

The Chelicerates

and

The Mandibulates

Chelicerate Arthropod Characters:

Pincher-like mouthparts - chelicerae - and pedipalps

NO antennae

Two body regions, usually - cephalothorax & abdomen

Four pairs of legs

Horseshoe crabs and arachnids are only living groups

Mandibulate Arthropod Characters:

Mouthparts are mandibles - normally chewing sideways

One or two pairs of antennae

Various body region arrangements - cephalothorax & abdomen / head & trunk / head, thorax & abdomen

Variable leg numbers

Insects, crustaceans & myriapods

Orders of Arachnids

Scorpiones - scorpions

Pseudoscorpiones - false scorpions

Opiliones - daddy-long-legs or harvestmen

Acari - mites & ticks

Araneae - spiders

Scorpion Tick(a mite)

Pseudoscorpion

Daddy-long-legs

WolfSpider

Scorpion Anatomy

chelicerae eyes pedipalp

Pseudoscorpion

pedipalps &chelicerae

cephalothorax

abdomen

Mite and Tick Body Regions

American dog tick male

Blacklegged (deer) tick female

American dog tick female laying egg mass (1000-2000 eggs!).

Clover mites

Twospotted spider mites

Predatory mite

Opiliones (=daddy-long-legs, harvestmen)

cephalothorax abdomen

pedipalp

chelicera (fang)

cephalothorax

abdomen

narrow waist

Spider Anatomy

Abdomen

Pedipalp

Chelicera (fang)

Cephalothorax

Jumping Spider

Wolf spider with egg case Spitting spider

Tarantula Orbweaving spider

Black widow with egg case

Brown recluse (fiddleback)

Classes of Myriapods(many legged arthropods)

(all have one pair of antennae, a head region, and trunk with many pairs of legs, use trachea)

Diplopoda - millipedes

Chilopoda - centipedes

Symphyla - garden centipedes

Myriapods

Millipede (Diplopoda)

Two pair of legs per visible segment, attached under body.

Centipede (Chilopoda)

Pair of fangs under head, one pair legs per visible segment - attached to side of body.

Symphylan (Symphyla)[garden centipede]

No fangs, no eyes, legs attached to side of body.

[one pair of antennae, head & trunk regions, trunk with many pairs of legs]

Millipede (Diplopoda)

Centipede (Chilopoda)

Garden centipede (Symphyla)

Classes of Crustacea(mostly marine, fresh water, a few terrestrial)

(all have two pair of antennae, five or more pairs of legs, segmented abdominal appendages, head & trunk or

cephalothorax & abdomen body arrangement, have gills)

Isopoda - sowbugs or pillbugs

Amphipoda - sand fleas, amphipods

Cirripedia - barnicles

Decapoda - crabs, lobster, shrimp

several other minor orders

Crayfish cephalothorax(Decapoda)

Sowbug (Isopoda), a terrestrial crustacean