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Northwest Wildlife Online
Phylum Arthropoda
Invertebrates with Chitinous Exoskeletons
Protozoans Sponges Cnidarians Ctenophores Arthropods Echinoderms Mollusks Nematodes Flatworms Annelid Worms
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Some of the more common of our myriad Arthropods. From left to right: a tiny marine crustacean, a Clown Millipede (Harpaphe haydeniana), a Jumping Spider (Platycryptus californicus). Below: a millipede of the family Nearctodesmidae scurries about; a Yellow Jacket (Vespulla spp.) scouts for new quarters, and a tiny Shore Crab (Hemigrapsus nudus) hunts for tasty barnacles to eat.
A Northern Kelp Crab, (sometimes referred to as a Spider Crab), Pugettia producta, photographed in Gig Harbor thanks to the assistance of Christopher, a budding young naturalist. This one is a male as evidenced by the the arrow shaped, white tipped, pointed abdomen on the ventral surface. Females have a much wider abdomen adapted for carrying eggs. Thanks Christopher!
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Four Subphylums, 12 Classes, 3 Subclasses, 2 Orders, and thousands of individual species of Phylum Arthropoda represent wildlife in the Northwest:
Subphylum Chelicerata
Class Merostomata - aquatic chelicerates
Class Pycnogonida - sea spiders
Class Arachnida - scorpions, spiders, mites, ticks, harvestman
Subphylum Hexapoda
Class Insecta - insects
Order Diplura
Order Protura
Subphylum Myriapoda
Class Chilopoda - centipedes
Class Diploda - millipedes
Class Pauropoda - pauropods
Class Symphyla - psuedo centipedes and symphylans
Subphylum Crustacea
Class Malacostraca - Crabs, krill, pill bugs, shrimp
Class Maxillopoda -
Class Branhchiopoda - branchipods
Class Ostracoda - ostracods
Class Cephalcarida -
Subclass Remipedia
Subclass Branchiura
Subclass Cirripedia - barnacles
Acorn Barnacles Balanus glandula. The most common barnacle in our area. Barnacles feed on microscopic creatures in the surf and in turn provide food for nudibranchs, crabs, and sea stars. What appear to be Black Turban snails are interspersed with the barnacles above. In the photo below a Giant Acorn Barnacle, Balanus nublis, sits among a cluster of mussels. To the bottom right is a cluster of Goose Barnacles, Pollicipes plymerus.
The Carpenter Ant (Camponotus spp). Growing to one half inch in length this is the largest ant in the Northwest. These guys do not sting, but as you can see, their mandibles are large and powerful. Not surprising for an insect that chews through wood to build a home.
Arthropods - the single most gigantic group of animals in the world. The arthropods make up more than 75% of all the known animal species in the world! Far more than a million species are presently recorded and an untold number await discovery. So you have to ask - what is the secret to their astounding success? Here are several factors:
1. Exoskeleton The external skeleton of arthropods could consume months of study. Every knows that arthropods have a tough, hard skeleton that covers the outside of their body. What is generally unknown is the ingenious composition of the exoskeleton. Composed of several layers: cuticle, endocuticle, and epicuticle, it is a combination of chitin, a substance similar to plant cellulose, bound with protein to form a complex glycoprotein. Further stabilized by the addition of other compounds, this covering can be a tough armor plating or a soft as a worn leather jacket.
2. Segmented Appendages Attached to strong internal muscles and coupled with the rigid exoskeleton arthropod legs are fast and efficient.
3. Respiration and Circulatory System Arthropods have an open circulatory system in which air is fed directly to tissues and cells through a system of tracheal tubes, a very effective mechanism for a small animal.
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The Cardinal Meadowhawk, Sympetrum ilotum, a member of the dragonfly family. For sheer deadly beauty these attack helicopters of the insect world are unsurpassed. The photos do not convey the rich cardinal red color of the Meadowhawk.
4. Sense Organs As anyone who has attempted to hand swat a fly can attest, arthropod senses are sharp. Hearing, sight, sense of smell, and touch are often extraordinary.
5. Behavior Patterns Are complex and often astonishingly coordinated in the social insects.
6. A Life of Change Many arthropods go through 2 or more stages as they mature, thus taking advantage of different environmental niches and kinds of foods.
Larvae of the Predacious Diving Beetle, of the Dytiscidae family. Well known as aggressive predators both in the larval and adult stage these guys will attack nearly anything; they've earned the nickname of Water Tigers. The photo above was taken in an alpine stream at about the 6,000 foot level in Mount Rainier National Park. To the right is a fine example of compound eyes, in this case from a dragonfly.
Pictured above are Formica obscuripes ants. These ants build large, numerous nest of small twigs and conifer needles, some over three feet high. Depending on the temperature the ants can be observed swarming in huge numbers. The close up photo on the right shows the coloration of F. obscuripes.
Common, yet incredibly complex and fascinating animals, the arthropods are an engrossing field of study. Enormously important to man for both good and bad economic reasons; behaviors and appearance that rival any science fiction tale; easily accessible to the amateur and ripe for new discoveries, this is tremendous window into wildlife wonder.
Protozoans Sponges Cnidarians Ctenophores Arthropods Echinoderms Mollusks Nematodes Flatworms Annelid Worms
Birds Mammals Reptiles Amphibians Fish Invertebrates Home
Mission Editor Bio Contact Wildlife Park Links Further Study Wild Employment Northwest Trek
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