Spiders are eight-legged arthropods and the largest order of arachnids known to be in existence at this time. All spiders share the same general characteristics, but there are a few significant differences between males and females. Sexing a spider can help in captivity as males need larger habitats, or in the wild because females are generally the venomous gender.
Female spiders are almost always larger than males, sometimes doubling the size of the males. Males, however, have longer legs. This is most likely an evolutionary characteristic as male spiders roam farther and more frequently than females. Males also have enlarged mouthparts, which sometimes look like a fifth set of legs. The males use the enlarged mouthpart to aid with sperm transfer during mating.
Like many animals, male spiders tend to be more brightly colored than female spiders. Males often have colorful spots or stripes running down their backs to attract the females. Males are always more patterned than females. The legs of a male especially, are usually marked by colorful stripes. Females, which must camouflage to protect their eggs and hatchlings, are usually a brown, gray or blackish color.
In venomous spiders, females tend to have larger venom sacs than males. In some species, adult males don't have functional venom sacs at all. Females need more venom to protect their nests, which is why they've developed large sacs. It is speculated that because many females don't leave their webs, they need more venom to subdue larger prey. Male spiders hunt while roaming and have more of a choice on what to eat.
For reasons unknown, female spiders live significantly longer than their male counterparts. Female tarantulas, for example, can live for up to 25 years. Males, on the other hand, rarely live longer than 10 years.