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insects, arachnids, crustaceans, myriapods phylum Arthropoda class Arachnida= Ametabolous = Hemimetabolous = Holometabolous= Beneficial = Benign = Pest= Herbivorous = Predaceous = Detritovorous= PollinatorDavid Cappaert, Michigan State Univ., Bugwood.orgKey characters are highlighted in blue. Follow the blue lines to see these characters in the photo-graph. Key characters are traits unique to one group of organisms that can be used to identify which group an organism belongs to. Since the centipede above has jointed legs and a hard exoskeleton, you know it is an arthropod. There are many key characters for every group, but only a few of the more easily seen ones will be highlighted here.All arthropods have a hard, chitinousexoskeleton which protects the softmembrane“Arthropoda” comes from arthro-, meaning jointed, and pod, meaning feet, or jointed legs taken together.ENT 4015: Orders of common landscape insects. Vera Krischik, Joel Gardner (TA).Photographs by Joel Gardner unless otherwise noted.spiders, scorpions, mites, harvestmenArachnids have eight legs (although some immature mites have only six) and two general body segments: the cephalothorax (fused head and thorax) and the abdomen. Sometimes the division between the two segments is so indistinct as to be unnoticeable (as in mites and harvestmen).spiders order AraneaeSpiders have a distinct cephalothorax and abdomen, one pair of chelicerae (fangs) with venom, one pair of pedipalps without venom (often larger and more easily seen), and a pair of spinnerets at the tip of the abdomen for spinning silk. Some spiders actively hunt and only spin silk in caring for eggs.mites and ticks subclass Acarispiders, scorpions, mites, harvestmen class Arachnida (continued)harvestmen/daddy longlegs order Opilionescentipedes class ChilopodaW.M. Ciesla, Forest Health Management International, Bugwood.orgClemson University - USDA CES, Bugwood.orgMites and ticks have one apparent body segment which is a fused cepha-lothorax and abdomen. Early instar nymphs have only six legs but are easily separated from insects by the one body segment and lack of antennae.Jerry A. Payne, USDA Agricultural Research Service, Bugwood.orgHarvestmen have one ap-parent body segment, similar to Acari. Most have very long legs, hence the common name “daddy longlegs”, although some predatory species have more spiderlike legs. Sep-arated from spiders by sin-gle body segment and lack of spinnerets.Centipedes have many body segments with one pair of legs per segment. The first pair of legs is modified into venomous fangs.Beneficial predatory mites can be distinguished from herbivorous pests by their movements. Predators will run quickly in a random search for prey, while pests tend to stay in one place and move only slowly.millipedes class Diplopodacrabs, lobsters, crayfish, shrimp, isopods subphylum Crustaceawoodlice, rock slaters order IsopodaHead, thorax, and abdomen may be vari-ously fused in different groups with dif-ferent numbers of segments. All crusta-ceans have two pairs of antennae (but this is extremely difficult to see in iso-pods).The only terrestrial crustaceans are isopods. Most com-monly encountered are woodlice (pillbugs and sowbugs). Pillbugs are rounder and can curl into a defensive ball; sowbugs are flatter and cannot roll up. All isopods have seven pairs of legs and breathe via gills underneath the abdomen.Millipedes have many body segments (usually more than centipedes) with two pairs of legs per segment (excluding the first three thoracic segments).Separated from centipedes by number of legs per segment and lack of fangs.insects, proturans, diplurans, springtails epiclass Hexapodaspringtails class Collembolainsects class Insectasilverfish, firebrats order ThysanuraClemson University - USDA CES, Bugwood.orgSusan Ellis, Bugwood.orgVery minute and often overlooked except when in large groups. Formerly classified as insects. Characterized by ventral appendage called the furcula which can spring the animal into the air—hence the name "springtails".“Hexa” means six and “poda” means feet—hexapods are characterized by having six legs. They also have distinct head, thorax, and abdomen segmentation, one pair of antennae, and a passive respira-tory system composed of tubes opening to the outside air through spriacles.Clemson University - USDA CES, Bugwood.orgPrimitive, wingless insects with flattened bod-ies covered with scales. Characterized by the three caudal filaments at the tip of the abdo-men. They are frequently pests when they in-habit homes.Joseph Berger, Bugwood.orginsects class Insecta (continued)grasshoppers, crickets, katydids order Orthopterapraying mantids order Mantodeacockroaches order BlattodeaClemson University - USDA CES, Bugwood.org Maja Jurc, University of Ljubljana, Bugwood.orgBeetlelike, but the wings are thin and membranous or ab-sent, and the pronotum extends over the head from above. Most spe-cies are benign; only six frequently infest hu-man dwellings.These insects are easily recognized by the en-larged hind legs modified for jumping (saltatorial). Wings, when present, are held roof-like over the abdomen. Forewings are thickened and leathery to protect membranous hindwings. Some adult grasshoppers have only vestigial wing pads and many crickets lack wings entirely.Mole crickets (family Gryllotalpidae) live underground and have modified forelegs with claws (fossorial) for digging.Johnny N. Dell, Bugwood.orgPraying (or preying) mantids are characterized by the highly modified forelegs used for catching and grasping prey (raptorial). Wings are similar to those of Orthoptera. Mantid egg cases (ootheca) are often placed in gardens as a means of biologi-cal control. However, the mantids will eat benefi-cial insects as well as pests.Joseph Berger, Bugwood.orginsects class Insecta (continued)termites order Isopteraearwigs order Dermapterabook lice, bark lice order PsocopteraJessica Lawrence, Eurofins Agroscience Services, Bugwood.orgDavid Cappaert, Michigan State University, Bugwood.orgSmall; often found in large groups on tree trunks. Despite large numbers, they are benign, feeding only on lichen and fungi. Distinguished by long, thin antennae and enlarged, “hump-backed” thorax. Wings are sometimes absent.Gary Alpert,


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