The spider most well known for having an orange spot underneath is the ventral orb weaver spider (Araneus ventricosus). This relatively common spider can be identified by the bright orange marking on its abdomen. In this article, we will discuss the key identification features, habitat, and behaviors of the ventral orb weaver to help identify this distinctive spider.
Spiders display an incredible diversity of shapes, sizes, and colors. While many spiders have more subdued coloration, some species sport bright patches of color on their bodies. One of the most recognizable is the ventral orb weaver, which has a vibrant orange spot or patch on the underside of its abdomen. This flashy marking makes the spider easy to identify once you know what to look for.
The ventral orb weaver is a medium-sized spider that spins circular webs for catching prey. It is found throughout much of North America and parts of Central America. The spider inhabits woodland edges, fields, gardens, and parks where it constructs its web among vegetation. While the ventral orb weaver is harmless to humans, its webs can become nuisance when built in areas frequented by people.
If you’ve noticed a spider with a blaze orange marking on its belly, chances are good it’s a ventral orb weaver. Read on to learn more about identifying this spider, including details on its appearance, web, habitat, range, and life cycle.
Appearance and Size
The most distinctive feature of the ventral orb weaver spider is the vibrant orange mark on the underside (ventral surface) of its abdomen. This may appear as a solid patch of color, broken patch, or concentrated spot. The orange area contrasts sharply with the otherwise brownish or grey body coloration. The intensity of the orange can vary between individual spiders. Scientists believe the marking may serve to attract prey to the web.
| Measurement | Size |
|---|---|
| Male body length | 5 – 9 mm |
| Female body length | 12 – 16 mm |
| Legspan | 25 – 40 mm |
Beyond the orange marking, ventral orb weavers have an oval-shaped abdomen and a small head region. The eight legs are slim and similar in length. Adult males are smaller than adult females.
Web
The ventral orb weaver constructs a classic orb web for catching prey. The web consists of a framework of non-sticky silk threads in a circular shape. A spiral of sticky silk threads is laid down in the center to trap insects. An open space near the edge of the web allows the spider to hide and wait for prey.
The webs are built 3-10 feet off the ground, attached to branches, twigs and plants. Orb webs are taken down each day and rebuilt in the evening. Web placement takes advantage of flight paths and areas where insects congregate. A messy tangle of silk may be present near the main web.
Habitat
Ventral orb weavers occupy open wooded areas including woodland edges, glades, riparian zones, and along hedges and trees. They are also found in fields, marshes, gardens, and parks. The spiders build their webs on low shrubs, tall grasses and herbaceous plants. Prime web placement includes sites near lights that attract night-flying insects.
The species ranges across much of North America from southern Canada south to Panama. It is more common in the eastern and central regions. Ventral orb weavers prefer warmer environments and are most active in summer and fall.
Life Cycle
The lifespan of ventral orb weavers is about one year. The spiders mate in late summer and fall. As with other orb weaver spiders, the much smaller male has specialized pedipalps for transferring sperm to the female.
Females lay eggs in a tan, papery egg sac attached to vegetation or debris. The egg sac may contain several hundred eggs. Spiderlings hatch in autumn but remain in the sac during winter. The young spiders disperse in spring and construct their first small webs. They will molt several times over the summer as they grow. Adult size is reached by late summer when mating occurs.
Diet
Ventral orb weavers prey on a variety of small insects that become caught in their sticky webs. Prime targets include flies, mosquitoes, moths, butterflies, beetles, grasshoppers, and flying ants and termites. The spider senses vibrations from insect impacts and rushes out from its hiding spot near the edge of the web to immobilize the prey by wrapping it in silk. The prey package is then carried back to the hub of the web where the spider can safely feed.
Bite Risk
Orb weaver spiders like the ventral orb weaver are not aggressive and rarely bite humans. Bites may occur from accidental contact with the web. The spider first tries to flee or play dead before resorting to biting in self-defense.
The venom of ventral orb weavers is considered only mildly toxic to humans. Bites result in minor and temporary effects including redness, mild pain, and localized swelling. Serious reactions are unlikely but heightened caution is advised for people with allergies to other venomous insects.
Other Orb Weavers to Check For
While the ventral orb weaver is the most likely suspect if you spot a spider with an orange marking, a couple other orb weavers have similar markings to be aware of:
Barn spider – Medium-sized brown and grey spider with bright orange underside. Makes its web in man-made structures.
Marbled orb weaver – Yellow and brown spider with orange/red marking on abdomen. Builds its web low in vegetation.
Orchard orb weaver – Greenish-yellow spider with red or orange stripe on abdomen. Occupies fruit trees and vines.
Conclusion
The ventral orb weaver’s distinctive orange marking makes this common backyard spider easy to identify. Now that you know where to look for the orange spot and what to expect from this species, keep an eye out for them in your neighborhood. Getting to know local spider species like the charismatic ventral orb weaver can help foster an appreciation for the diversity and beneficial roles of spiders in the environment. If you spot one, take a moment to admire its colorful pattern before allowing it to go on its way.
