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How to Identify a Spider With Black Joints

Many spiders are predominantly black or otherwise dark, especially as viewed by a much larger human being. Others that are lighter-colored might have black stripes or banding on their legs. Either way, a black-jointed spider could belong to any number of species. It might be a minuscule cobweb spider hidden at the corner of a high ceiling, or a massive tarantula clambering across white-sand flats. Identifying the spider means considering both physical and behavioral traits. This takes an acute eye, patience and the composure to study carefully this mostly harmless and beneficial order of arachnids.

Instructions

- 1
  
  Many tarantulas show black joints on thick, hairy legs.
  
  Consider the thickness of the legs surrounding the joints. Certain spiders have proportionately robust limbs. Tarantulas, many of which are predominantly black with a huge range of colorful patterns, have thick, rubbery-looking legs, for example. A black widow's, in comparison, appear thread-thin.
- 2
  Look at the length of the legs. Jumping spiders often have black joints, but their legs, unlike those of many spiders, are usually held close to the body and are relatively short. Indeed, many roughly resemble a hermit crab in structure. A garden spider will have much longer limbs in proportion to its body, splayed out as it waits in ambush on the strands of its web (if it is a female, which are more conspicuous and more commonly seen).
- 3
  Study the shape of the spider. Trapdoor spiders, found across much of North America and related to tarantulas, have formidably large jaws (in addition to thick legs). A shamrock orbweaver, which has black banding on its legs, has a massive abdomen in proportion to the rest of its body.
- 4
  
  Garden spiders with black joints are often observed as females in large webs.
  
  Consider the spider's behavior and general habitat. A female black widow will usually be seen ensconced in a web in some dark, out-of-the-way place such as a cellar corner or a wood-pile. A jumping spider, which is not a nest-builder, will be actively roaming in search of prey.
- 5
  Use a magnifying glass to discern other physical features that will help you at least identify a spider to a family. For example, the arrangement of a spider's eyes can often get you this far. You might also look at coloration patterns beyond the black knobs of the legs, as well as relative proportions of the body segments.

Animals & Science