Spider ID


Eye patterns are distinctive for different spider families.
Drawings © 1999 Eric Parrish

a) Salticidae, or the jumping spiders;
b) Lycosidae, or the wolf spiders;
c) Araneidae, or the orb-weaving spiders;
d) Thomisidae, or the crab spiders;
e) Dysderidae; f) Pholcidae, or the daddy-long-legs spiders.

If the spider you are trying to key out does not fit one of these eye patterns, refer to the Dichotomous Key to Spider Families.

Dichotomous Key

A dichotomous key is arranged as paired couplets. With the specimen in front of you (and some means of magnifying the specimen), read through the first couplet designated 1a and 1b. If all the characteristics of 1a better describe your specimen, then proceed to the couplet number indicated at the end of the line. If the characteristics listed under 1b better describe the specimen, then proceed to a different couplet indicated at the end of that line. Continue in this manner until you are led to a family name. Some of the characters in the key refer to web characteristics, behavioral characteristics, or to the habitat in which the spider was found. Therefore, it is a good idea to take note (a literal note or a mental note) of these traits for the different specimens you collect. It is useful to carry a field notebook with you for such purposes.

Roman numerals are used to indicate a particular leg. Leg I is the leg nearest the eyes while Leg IV is the leg nearest the abdomen. The word anterior means closer to the cephalothorax while posterior means closer to the spinnerets. The word dorsal means on the top side of the animal while the word ventral refers to the "belly" side.

Dichotomous Key to the Common Families of Colorado Spiders
(derived from Kaston, B.J. 1978. How to Know the Spiders. The Pictured Key Nature Series, Wm. C. Brown Co. Publishers, Dubuque, Iowa.)

Drawings © 1999 Eric Parrish


 Parallel fangs and rastellum on the chelicerae of mygalomorph spiders.


Fangs on the chelicerae of labidogath spiders.


1a) Suborder Orthognatha or Mygalomorpha"

  • Fangs, or chelicerae, move more or less parallel to one another (Fig. 8).
  • Two pairs of lungs evident as slit-like structures on the ventral surface of the abdomen.
  • Fairly large, robust "tarantula" spiders.
  • These spiders will only be found in the southern portion of the state. 2

1b) Suborder Labidognatha

  • Chelicerae move in opposition (Fig. 9).
  • Most spiders encountered in Colorado will fall into this Suborder. 3


Claw tufts and scopula of a tarantula.

 2a ) CTENIZIDAE (Trapdoor spiders)
  • Tarsi with two large lateral, or side, claws on the tarsi and one small median, or middle, claw.
  • No claw tufts evident. A rastellum (see Fig. 8) evident on the chelicerae.
  • Spiders are usually found in burrows hinged with a lid made from soil and lined with silk (as is the burrow).
  • The trapdoor is often very well camouflaged with bits of leaves and other material.
  • Males often wander outside the burrows after heavy rains from November to February.

2b) THERAPHOSIDAE (Hairy mygalomorphs or Tarantulas)

  • Spider covered with hairs.
  • Tarsi with claw tufts and scopula (Fig. 10). Without rastellum on the chelicerae.
  • Mostly active at night.
  • Males often wander in search of females from July to November


 Cribellum anterior to the spinnerets on a cribellate spider


 The calamistrum is used for drawing silk out of the cribellum

 3a ) Cribellate Spiders
  • A specialized spinning plate, called a cribellum (Fig. 11) is located anterior to the spinnerets in females and juveniles.
  • A specialized comb of bristles, called a calamistrum (Fig 12) is located on metatarsus IV of females and juveniles.
  • Remnants of the cribellum or the calamistrum can sometimes be seen on adult males.
  • Webs of these spiders often have a bluish sheen. 4

3b) Ecribellate Spiders

  • Spider lacks both the cribellum and the calamistrum. 9
 Figure3f  4a) HYPOCHILIDAE (Lamp shade spider)
  • Two pairs of book lungs present.
  • Adult females and juveniles construct irregular mesh webs under rock overhangs.
  • The webs are often shaped like a lamp shade with the spider resting in the center of the shade (Fig. 3f).
  • Found in the mountainous areas of Colorado. Uncommon.


4b) With only one pair of lungs or no lungs. 5


 The cribellum and the fringed anal tubercle of an oecobiid


 Carapace of an oecobiid.

  • Tiny spiders (2 to 2.5 mm long).
  • Anal tubercle is prominent and has a fringe of long hairs (Fig. 13).
  • Posterior median eyes are irregularly shaped.
  • The carapace is round (Fig. 14)

5b) No fringe of hairs near the anal tubercle. Posterior median eyes are circular. Spiders may be 2mm or larger. 6


 Fused labium of the Filistatidae.



  • The labium is fused to the sternum (Fig. 15) and the calamistrum on the females and juveniles is short, made up of only a few stiff bristles.
  • Spiders hide in a tubular retreat with silk lines radiating from the opening. Uncommon spider.


  • Labium is separate from the sternum (see Fig. 1).
  • The calamistrum is longer than described in 6a.
  • All eight eyes are light in color.
  • Spiders usually found under logs or stones where they build a messy, irregularly shaped web

7b) All eyes are either dark or the spider has a mixture of light and dark eyes or the spider has only six eyes. 8



  • All eyes dark.
  • Spiders either build round orb webs or triangular-shaped webs


  • Eyes vary; some dark some light.
  • Spider may have only six very white eyes.
  • Spiders usually found in small, messy webs at the tips of vegetation, especially in grassy fields.
  • Can also be found under stones and dead leaves. Represents the most species-rich family of cribellate spiders


Remember that most spiders have spiny legs. To be a mimetid, the spider must have spines arranged in the pattern illustrated.

9a) MIMETIDAE (Pirate spiders)
  • Tibia and metatarsus I and II have a row of long spines.
  • In between the large spines is a row of shorter, curved spines (Fig. 16).
  • These spiders feed on other spiders and can be found at the edges or near the webs of other spiders.
  • Sometimes they wait beneath leaves ready to ambush passing spiders.
  • These are slow-moving spiders

9b) Metatarsus and tibia I and II without such spines. 10


Flexible tarsus of a pholcid.

10a) PHOLCIDAE (Daddy-long-legs spiders)
  • Tarsi long and flexible, appearing to have many little segments (Fig. 17).
  • Spider has long thin legs and a long narrow abdomen.
  • Often found in irregular webs in cellars or other dark locations.
  • Spider sometimes vibrates rapidly when disturbed

10b) Tarsi not as described above. 11

  11a) Spider has six eyes. 12

11b) Spider with eight eyes. 13




 Four respiratory slits of Dysdera crocata (family Dysderidae).


 Claw tufts of Dysdera(Dysderidae)



  • Appears to have four lung slits on the ventral surface of the abdomen (Fig. 18).
  • Tarsi with two claws and with claw tufts (claw tufts may obscure claws) (Fig. 19).
  • Legs I and II directed forward while legs III and IV are directed back.
  • Cephalothorax dark reddish brown and abdomen greyish tan with orange legs.
  • Large jaws evident (adapted for hunting pillbugs).
  • Eyes and jaws as in Fig. 7e


  • Spider with only two respiratory (book lung) slits.
  • Tarsi with three claws and no claw tufts (Fig. 20).
  • Legs I, II, and III directed forward; only legs IV directed back. Body and leg color not as in 12a


Three tarsal claws of a web-building spider.


  • Spider with two claws and claw tufts (Fig. 19) or with two claws and no claw tufts. (If claw tufts are present, then you can assume the spider has only two claws.)
  • These are primarily the wandering spiders. Most do not build webs to capture prey. 14


  • Tarsi have three claws and no claw tufts (Fig 20). These are mostly web-building spiders.
  • The third (middle) claw is used to grasp the silk lines of the prey capture web. 19





14a) (Jumping spiders) SALTICIDAE
  • The anterior median eyes of the spider are much larger than the other six eyes (Fig. 7a).
  • These spiders are active during the day and have keen eyesight. The chelicerae are often brightly colored.


  • Eyes not as described in 14a.
  • Anterior median eyes not considerably larger than the rest of the eyes. 15


Position of the tracheal spiracle of an anyphaenid.

  • Tracheal spiracle closer to the center of the abdomen than to the spinnerets (Fig. 21).
  • Most of the spiders in this family are pale yellow or white in color.


  • Tracheal spiracle located just anterior to the spinnerets as it is in most spiders.
  • Spiders usually darker in color. 16


Lateral position of legs I and II of crab spiders.

  • Legs I and II (at least) held to the side of the body like a crab rather than held in front of the spider (Fig. 22).
  • Spiders often found on flowers. 17


  • Legs I and II held more anteriorly rather than laterally. 18
 Crabspider 17a) (Crab spiders) THOMISIDAE
  • Legs I and II longer and more robust than legs III and IV

17b) PHILODROMIDAE (Philodromid crab spiders)

  • All legs about the same length or leg II much longer than legs I, III, and IV


Cylindrical, separated anterior spinnerets of a gnaphosid (dorsal view)


Eye pattern of a gnaphosid.


Ventral view of the endites of a gnaphosid.


A close-up view of a spider's spinnerets.

  • Anterior spinnerets cylindrical and separated by a distance about equal to the diameter of one cylindrical spinneret (Fig. 23).
  • Anterior median eyes dark; other eyes light. Posterior median eyes often oval or more or less triangular rather than circular (Fig. 24).
  • Endites are depressed or somewhat pinched in the center (Fig. 25).
  • Spiders often found under stones or logs.
  • Usually dark-colored spiders.

18b) CLUBIONIDAE (Sac spiders)

  • Anterior spinnerets conical and contiguous (or nearly contiguous) (Fig. 2).
  • Endites in most without a depression near the center. Often found in similar habitats as gnaphosids.


Eye arrangement of an oxyopid.
19a) OXYOPIDAE (Lynx spiders)
  • Eyes arranged in a hexagonal pattern (Fig. 26). Abdomen pointed posteriorly and legs with prominent spines. Although spiders have three claws, they do not build webs and are found on low bushes and vegetation.

19b) Eye arrangement not in a hexagon. 20


Serrated comb on the tarsus of leg IV of a theridiid.


20a) THERIDIIDAE (Cobweb weavers or Combfooted spiders)
  • Tarsus IV with a ventral comb made up of 6 to 10 serrated bristles (Fig. 27).
  • Females found hanging upside down in an irregular cobweb (Fig. 3c) (males often at the edge of the webs).
  • Females often with a bulbous abdomen. Black widow spiders are in this family.


  • Tarsus IV without a ventral comb. 21


A rebordered labium.






  • Edge of the labium is rebordered (Fig. 28).
  • Many of these spiders build webs as in Fig. 3a, d, or e or are tiny spiders found in somewhat messy webs near the ground (this latter group common in pitfall traps). 24


  • Labium not rebordered.
  • These spiders often large and either build webs as in Fig. 3b or are non-web-building (wandering) spiders. 22


Notched trochanter (ventral view).


22a) All trochanters with a curved notch that can be seen on the ventral side of the trochanter (Fig. 29). 23

22b) AGELENIDAE (Funnel weavers)

  • Trochanters are not notched.
  • Most of the spiders in this family are found living in sheet webs with a funnel-like retreat (see Fig. 3b).





Eye arrangement of a pisaurid spider.



23a) LYCOSIDAE (Wolf spiders)
  • Eyes as in Fig. 7b.
  • Posterior eyes larger than anterior eyes with posterior median eyes larger than other eyes and posterior lateral eyes seeming to form a third row.
  • Posterior median and posterior lateral eyes arranged as a trapezoid.
  • Female spiders carry the eggsac attached to the spinnerets and, when the eggsac hatches, the spiderlings crawl up onto the female's abdomen.
  • Most spiders active at night and eyeshine can be seen using a headlamp.
  • Spiders are wandering spiders that use their keen eyesight to locate prey.

23b) PISAURIDAE (Fishing spiders or Nursery web spiders)

  • Overall body shape similar to the Lycosidae. However, posterior lateral eyes not forming an apparent third row (Fig. 30).
  • Posterior median eyes only slightly or not at all larger than anterior median eyes.
  • Female holds the eggsac beneath the cephalothorax.
  • Spiderlings not carried around by the mother. When the eggsac is about to hatch, the female ties it amongst vegetation and sits in guard until the young disperse.
  • These are also wandering spiders.
  • They spend most of their time near water or streams.






  • All eight eyes approximately the same size.
  • Chelicera with a boss (Fig. 7c).
  • Boss may be rudimentary, but, if so, the chelicerae are generally long and robust.
  • Most females construct orb webs (see Fig. 3a). 25

  • Eyes not all the same size.
  • Chelicera with no boss.
  • Most construct some form of tangled web, bowl-and-doily web, or a tent-shaped web (see Fig. 3c, 3d, or 3e), not flat orb webs 26


Chelicerae of a tetragnathid spider.



25a) TETRAGNATHIDAE (Long jawed spiders)
  • Spiders usually found near water.
  • Boss may be rudimentary and difficult to see.
  • Most species have large and robust chelicerae (Fig. 31)

25b) ARANEIDAE (Orb-weavers)

  • Boss conspicuous on the chelicerae (see Fig. 7c).
  • Spider with eye arrangement as in Fig. 7c.
  • Most species build orb webs (see Fig. 3a)


Truncate sternum of a theridiosomatid.


 Stridulating area on the lateral surface of a chelicera of a linyphiid spider


26a) THERIDIOSOMATIDAE (Ray spiders)

  • Tiny, relatively uncommon spiders with a broadly truncate sternum (Fig. 32).
  • Abdomen globular, shaped somewhat like the abdomen of a theridiid spider.
  • Chelicerae lack a stridulating area on the lateral surface (Fig. 33 shows a stridulating area).
  • Females hold up the center of the orb web so it is shaped like a tent (Fig. 3d)

26b) LINYPHIIDAE (Sheet-web weavers)

  • Lateral face of the chelicerae with a stridulating area used, presumably, in courtship (Fig. 33).
  • Webs not as in 26a. Mostly small spiders (less than _ inch). Very large, common familyon the lateral surface of a chelicera of a linyphiid spider
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