Entomology 101 Arthropod Groups David J. Shetlar, Ph.D. The “BugDoc” The Ohio State University, OARDC & OSU Extension Columbus, OH © Sept, 2009, D.J. Shetlar, all rights reserved

Characteristics of the Phylum Arthropoda Coelomate protostomates that posses a segmented chitinous exoskeleton that must be shed during growth. Segments have paired appendages (e.g., legs, antennae) that are jointed. Segments are grouped into regions, called tagmata (e.g., head, thorax, abdomen). The nervous system is ventral The circulatory system is open and dorsal.

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

Classes of Arthropods: Chelicerates – Class Xiphosura – horseshoe crabs Class Arachnica – arachnids Mandibulates – Class Crustacea – crustaceans Class Diplopoda – millipedes Class Chilopoda – centipedes Class Symphyla – garden centipedes Class Hexapoda – insects

Class Arachnida 2 body regions Cephalothorax Abdomen

Major 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 Wolf Spider

Order Scorpiones { pedipalps

chelicerae eyespedipalp

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 ( eggs!).

Clover mites Twospotted spider mites Predatory mite

Opiliones (=daddy-long-legs, harvestmen) cephalothoraxabdomen

pedipalp chelicera (fang) cephalothorax abdomen narrow waist Spider Anatomy

Abdomen Pedipalp Chelicera (fang) Cephalothorax Jumping Spider

Wolf spider with egg caseSpitting 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 External Morphology

Sowbugs (Isopoda), terrestrial crustaceans