The arthropods are the most successful type of organism known so far - if you define success by the number of known species. Almost half of the described species are arthropods, and given the rate at which scientists find new species, we can presume that we have described less than one fifth of the species out there. They are bilaterally symmetrical (there is a left/right symmetry), their bodies are made up from a series of segments, and they have paired and usually jointed appendages on some or all of the body segments. The body is protected by a tough organic or organic-mineral cuticle which functions as an exoskeleton. In order to grow, arthropods periodically shed their cuticle by a process called ecdysis. Insects, spiders, crustacea, trilobites are all types of arthropods.

Arthropoda is prey of:
Charadriiformes
Calcarius
Eremophila alpestris
Calcarius mccownii
Spermophilus
Peromyscus maniculatus
Orthoptera
Athene cunicularia
soil micropredators
Arthropoda
facultative hyperparisitoids
Reptilia
Mammalia
Aves
Serpentes
Sauria
Perca flavescens
Ambloplites rupestris
Lepomis megalotis
Etheostoma caeruleum
Rana okaloosae
Bufo americanus
Bufo marinus
Dendrobates auratus
Ambystoma annulatum
Anolis equestris
Basiliscus vittatus
Cyclura cornuta
Podilymbus podiceps
Butorides virescens
Egretta tricolor
Anas strepera
Anas cyanoptera
Anas americana
Aix sponsa
Falco biarmicus
Grus japonensis
Gallinula chloropus
Actitis macularia
Recurvirostra americana
Cuculus canorus
Otus asio
Otus trichopsis
Strix varia
Chaetura pelagica
Lampornis clemenciae
Amazilia tzacatl
Tyrannus forficatus
Pyrocephalus rubinus
Auriparus flaviceps
Certhia americana
Dendroica petechia
Dendroica magnolia
Wilsonia citrina
Agelaius phoeniceus
Junco hyemalis
Passerella iliaca
Plectrophenax nivalis
Sturnus vulgaris
Corvus corax
Corvus caurinus
Polioptila melanura
Sorex dispar
Sorex gaspensis
Sorex merriami
Suncus murinus
Neurotrichus gibbsii
Parascalops breweri
Myotis grisescens
Sciurus niger
Tamias dorsalis
Peromyscus gossypinus
Peromyscus boylii
Peromyscus truei
Rattus exulans
Onychomys arenicola
Lontra canadensis
Nasua nasua
Cerdocyon thous
Paleosuchus trigonatus
Chaetodipus formosus
Dasycercus cristicauda
Planigale tenuirostris
Prionailurus viverrinus
Mellisuga helenae
Otus kennicottii
Pulsatrix perspicillata
Euoticus elegantulus
Galago alleni
Saguinus bicolor
Cebus olivaceus
Saimiri oerstedii
Papio hamadryas
Macroscelides proboscideus
Dryomys nitedula
Hydromys chrysogaster
Pseudomys higginsi
Heloderma horridum
Gymnobelideus leadbeateri
Pseudalopex griseus
Pseudalopex vetulus
Prionailurus planiceps
Mungotictis decemlineata
Crossarchus obscurus
Herpestes edwardsii
Herpestes ichneumon
Suricata suricatta
Amblonyx cinereus
Lontra provocax
Melogale everetti
Melogale personata
Mydaus marchei
Conepatus chinga
Conepatus semistriatus
Galictis cuja
Martes melampus
Mustela altaica
Mustela putorius
Mustela sibirica
Bassaricyon gabbii
Sus celebensis
Rhinosciurus laticaudatus
Sundasciurus hippurus
Petaurista elegans
Dendromus mystacalis
Tatera indica
Chaetophractus villosus
Solenodon paradoxus
Limnogale mergulus
Potamogale velox
Hemiechinus aethiopicus
Nectogale elegans
Plecotus auritus
Hipposideros diadema
Megaderma lyra
Argiope aurantia
Canis lupus familiaris
Papio ursinus

Based on studies in:
USA: Alaska, Barrow (Tundra)
USA: California, Cabrillo Point (Grassland)
USA: California, Coachella Valley (Desert or dune)
USA: Wisconsin, Little Rock Lake (Lake or pond)

This list may not be complete but is based on published studies.

Arthropoda preys on:
saprovores
Plantae
detritus
soil micropredators
Arthropoda
carcass
Sphaeromais
Clinotanypus
Guttipelopia
Corynoneura
Nanocladius
Cryptochironomus
Microtendipes
Paratendipes
Pseudochironomus
Xenochironomus
Eoparagyractis
Chaoborus punctipennis
Albabesmyia
Djalmabatista
Larsia
Macropelopis
Procladius
Chaetocladius
Cricotopus
Micropsectra
Paratanytarsus
Tanytarsus
Cladopelma
Endochrionomus
Glyptotendipes
Parachironomus
Polypedilum
Stenochironomus
Oligochaeta

Based on studies in:
USA: Alaska, Barrow (Tundra)
USA: California, Coachella Valley (Desert or dune)
USA: Wisconsin, Little Rock Lake (Lake or pond)

This list may not be complete but is based on published studies.

Animal / predator
Aeolothrips albicinctus is predator of Arthropoda
Remarks: Other: uncertain

Animal / predator
Aeolothrips melaleucus is predator of Arthropoda
Remarks: Other: uncertain

Animal / predator
Aeolothrips versicolor is predator of Arthropoda

Animal / predator
Aeolothrips vittatus is predator of Arthropoda
Remarks: Other: uncertain

Animal / predator
larva of Haplothrips subtilissimus is predator of Arthropoda
Remarks: season: 8-9
Other: uncertain

Animal / predator
larva of Hoplothrips longisetis is predator of Arthropoda
Remarks: season: 3-4,8-9
Other: uncertain

In Great Britain and/or Ireland:
Animal / pathogen
Metarhizium anamorph of Metarhizium anisopliae infects Arthropoda

Minerals conserved during moult: crustaceans
 

Crustaceans conserve minerals when moulting by absorbing calcium carbonate from their shell before it is shed.

       
  "The external shell gives the crustaceans the problem it gave the trilobites. It will not expand and since it completely encloses their bodies, the only way they can grow is to shed it periodically. As the time for the moult approaches, the animal absorbs much of the calcium carbonate from its shell into its blood. It secretes a new, soft wrinkled skin beneath the shell. The outgrown armour splits and the animal pulls itself out, leaving it more or less complete, like a translucent ghost of its former self. Now its skin is soft and it must hide, but it grows fast and swells its body by absorbing water and stretching out the wrinkles of its new carapace. Gradually this hardens and the animal can again venture into a hostile world." (Attenborough 1979:58)
  Learn more about this functional adaptation.

Multiple joints allow circular movement: crustaceans
 

Limbs of crustaceans allow movement along several planes by clustering two or three joints on a limb, each working in a different direction.

       
  "The limbs, which are tubular and jointed, are operated by internal muscles. These extend from the end of one section, along its length, to a prong from the next section which projects across the joint. When the muscle contracts between these two attachment points, the limb hinges. Such joints can only move in one plane, but crustaceans deal with that limitation by grouping two or three on a limb, sometimes close together, each working in a different plane so that the end of the limb can move in a complete circle." (Attenborough 1979:58)
  Learn more about this functional adaptation.

Joints have two degrees of bending freedom: arthropods
 

The joints of some arthropods have two degrees of bending freedom (up-down and left-right) thanks to two 1-degree bending joints found at right angles to each other.

         
  "Bending both up-down and left-right…Arthropods gain two degrees of bending freedom by putting two 1-degree bending joints next to each other, each oriented at a right angle to the other…The classic work on such cases was done by S.M. Manton, in the 1950s and 1960s; as put, with a long list of references, by Wainwright et al. (1976), 'The accounts of her researches in this field constitute a monument in the study of mechanical design of the most mechanically diverse group of organisms that have ever lived.'" (Vogel 2003:403)
  Learn more about this functional adaptation.

Cuticle provides protection: arthropods
 

The cuticle of arthropods provides rigid protection via its composite structure.

     
  "What we're calling rigid materials includes a lot of familiar biological items. There's arthropod cuticle, a composite of chitin fibers in some proteinaceous material, with the addition of calcium carbonate salt in the larger crustaceans. In many instances, the fibers are arranged in sheets, each with a specific orientation, rather like plywood." (Vogel 2003:305)
  Learn more about this functional adaptation.