Spiders (Araneae) are a large group of animals usually with eight legs. Most spiders spin webs to catch their prey. There are about 3,000 species of spiders in the United States.

Arachnid (Class Arachnidae) consists of nine to eleven different surviving orders depending upon how one divides the Arachnid class. In total, there are about 100,000 to perhaps 105,000 species grouped in the following eleven orders:

Order - - - - - - - Number of Species

Acarina-Mites and Ticks - 30,000 to 48,000
Amblypygi-Tailless Whipscorpions - 60
Araneae-Spiders - 35,000 to 40,000 (2016)
Palpigrada-Micro Whipscorpions - 50
Ricinulei or Podogona-Ricinulids - 20
Pseudoscorpionida-False Scorpions - 1,000
Schizomida-Short Tailed Whipscorpions - --
Scorpionida-Scorpions - 2,000 to 1,286 (2016)
Solpugida-Sun Spiders, Windscorpions - 1,000
Phalangida-Daddy Long Legs-Opioiones- - 2,200 to 5,000 (2016)
Uropygi-Whipscorpions - 70 to 130 (2016)

The old order, Pedipalpida (Whipscorpions), has been divided into the following orders:
Uropygi - (Whipscorpions)
Ambylypygi - (Tailless Whipscorpions)
Schizomida - (Short Tailed Whipscorpions)

Jointed Legged Animals (Phylum Arthropoda) make up the largest phylum. There are probably more than one million different species of arthropods known to science. It is also the most successful animal phylum in terms of the total number of living organisms.

Butterflies, beetles, grasshoppers, various insects, spiders, and crabs are well-known arthropods.

The phylum is usually broken into the following five main classes:
Arachnida: - Spiders and Scorpions
Crustacea: - Crabs and Crayfish
Chilopoda: - Centipedes
Diplopoda: - Millipedes
Insecta: - Insects

There are several other "rare" classes in the arthropods that should be mentioned. A more formal list is as follows:

Sub Phylum Chelicerata
C. Arachnida: - Spiders and scorpions
C. Pycnogonida: - Sea spiders (500 species)
C. Merostomata: - Mostly fossil species

Sub Phylum Mandibulata
C. Crustacea: - Crabs and crayfish

Myriapod Group
C. Chilopoda: - Centipedes
C. Diplopoda: - Millipedes
C. Pauropoda: - Tiny millipede-like
C. Symphyla: - Garden centipedes

Insect Group
C. Insecta: - Insects

The above list does not include some extinct classes of Arthropods such as the Trilobites.

Animal Kingdom contains numerous organisms that feed on other animals or plants. Included in the animal kingdom are the lower marine invertebrates such as sponges and corals, the jointed legged animals such as insects and spiders, and the backboned animals such as fish, amphibians, reptiles, birds, and mammals.

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