( Araneae )



(Hentz, 1757)
Common Name:Spider
Life Stage:(A) adult


Taxon Code:ARA01390
ITIS TSN#:82732

29629 Mountain Oak Ct., 0003, 29629 Mountain Oak Ct., Hayward
County:Alameda County
ECI Site#:CA01070003

Sex: Look at the front of your specimen, where the face of the spider is. You will find two small appendages that resemble little legs. These appendages are called pedipalps, and are used for sensing the spider's immediate environment, for assisting with eating, and for males, reproduction (specifically sperm deposition). Please refer to the Anatomy section above for a picture of a spider with the pedipalps labeled. If the pedipalps resemble boxing gloves (the tips of the pedipalps are swollen), it is an adult male. Here is an example of an adult male (Agelenopsis grass spider): If the pedipalps are not swollen, it is either a female, or an immature of either sex. (Characteristics of the female genital opening, the epigynum, may be used for species-level identification.) At this point, more information is needed about the spider (shape, size, location, coloration, style of web, etc.); this information can be used to determine the maturity level of the spider, which would indicate whether it is an adult female or an immature spider of either sex. ?Review of the common families represented in the Guide ?A guide to easily identifiable spiders:; a good inexpensive guide to common spiders and other arachnids: ?Two body parts: cephalothorax and abdomen ?Eight legs attached to cephalothorax. Recognition: Visible silk Glands.

Spiders eat whatever insects are available in their environment. Web-making spiders catch their prey with a web, whereas hunting spiders ambush their prey without the use of a web. Every species of spider is uniquely evolved to fit its environment. Spiders in hot, dry climates can last longer without water than a spider from a super humid climate. Also, spiders that are synanthropic (associated with human habitation) have evolved to survive indoors where typically little or no water is available and food is less plentiful.
Life Cycle: There are a few different ways or terms to describe a spider's life cycle. One could delve into such terms as prelarva and postembryonic if one wanted, but here is the gist of it: Egg--> Spiderling--> Immature/juvenile/subadult--> Penultimate--> Adult. Spiders must shed their exoskeleton, or molt, in order to grow. They will molt as many times as is needed (approx 4-12) to reach adulthood. The penultimate stage can most simply be described as 'next to last'. A penultimate spider has signs of underdeveloped genitalia and needs only one last molt to become adult. After that last molt, the genitalia is fully revealed and entirely developed. True spiders, or araneomorphs, will not molt past adulthood. Their next step is, eventually and inevitably, death. That is in contrast to the mygalomorph spiders who live much, much longer and continue to molt once or twice a year through their long adult lives.
While it's true that most have venom (the single exception in our area: Cribellate Orb Weavers in the Family Uloboridae) the bites of all but a few are only mildly painful, and have no lasting effects. Believe it or not, almost all species are not harmful to people, but are actually beneficial because they catch and eat a lot of insects that can be pests. Spiders do not seek out, chase, or randomly attack people, nor do they carry grudges against people. If you leave them alone, they will leave you alone. Most people are bitten because they were playing with the spider (which is effectively asking to be bitten), or the spider felt threatened without a chance to escape; many times, surprising the spider was completely accidental. Depending on your geographical location, there are only a few spiders that you need to be familiar/concerned with (see the comments below on the spiders of potential medical concern). If you aren't sure whether the spider you have might be harmful, leave it alone and do not kill it. If you have to move it, please refer to the Relocating The Spider comments below. Spiders of Potential Medical Concern: ?Black Widow (Latrodectus spp.). ?Brown Recluse (Loxosceles reclusa). ?Yellow Sac Spider aka Longlegged Sac Spider (Cheiracanthium spp.): this is probably not true and is based on lab experiments on rodents, not HUMANS! Please read this paper that shows their venom is not necrotic to human cells. ?Hobo Spider (Tegenaria agrestis): this, also, was based on lab experiments on rodents, not HUMANS. A Hobo spider hasn't even ever been verified as the culprit in any spider bites on humans, despite all the rumors and misconstrued information that you'll hear! In the most recent literature, this spider is AGAIN shown to NOT BE MEDICALLY SIGNIFICANT. Please read this paper by clicking free PDF located directly under View Now.


Eddie Dunbar

  • BugGuide [ IMAGES ]
  • Integrated Taxonomic Information System TSN#82732