Wild Facts About The Marbled Orb Weaver Spider
How To Identify Marbled Orb Weaver Spiders
- Like many spiders, Marbled Orb Weavers are sexually dimorphic, with the females growing much larger than the males.
- Female Marbled Orb Weaver spiders grow to 0.7 inches (1.8 cm) in total body length.
- Male orb weavers are about a third as long, growing to only 0.2 inches (0.6 cm).
- Female Marbled Orb Weavers are distinctive thanks to their size, bright colors, and very large, round abdomens.
- Their cephalothoraxes are bright orange.
- Their legs are orange at the bases, and banded in white and black to the tips.
- Their abdomens vary in color and pattern. In North Carolina, these spiders usually have bright yellow or orange abdomens decorated with zig-zag blotches of black or dark brown.
- Juvenile spiders tend to be more pale overall (Bradley 2012).
- Compared to female orb weavers, male Marbled Orb Weavers:
- Are less colorful and more uniformly orange.
- Also show bands of color on their legs but the bands are shades of orange and cream so are less distinct.
- Are much skinnier overall.
- Males lack the females’ large, bulbous abdomens, as they do not carry organs required for laying eggs. The abdomens on male Marbled Orb Weavers are thin, flattened, and smaller than their cephalothoraxes.
Taking It Down To Put It Back Up Again
Marbled Orb Weaver spiders spin large capture webs to trap flying insects. But they don’t simply spin their webs once and then just sit around and wait. Every day, these spiders take down and eat the previous day’s web, then build an entire, fresh web.
Eating the previous day’s web silk preserves the spiders’ resources; they can recycle the nutrients and water required for spinning the silk strands from the previous day’s web.
But the benefit of daily web recycling doesn’t stop with just recovering the previous day’s resources. Instead, the Marbled Orb Weaver’s habit of eating its web daily before rebuilding actually helps them get more water than they started with.
The capture strands of an orb weaver’s web are composite threads composed of a fiber coated with regularly spaced, aqueous, adhesive droplets, to which insects that collide with the web become stuck.
These adhesive droplets attract water. Marbled Orb Weavers eat their webs during periods of high humidity when their existing webs contain more water volume than the spiders contributed originally.
The contribution of water volume from humidity captured by the web strands is probably small compared to the spiders’ intake from their food; “high estimates of the net water gained range from 0.45% of a spider’s body mass (3.01µl water gained) in A. marmoreus to 0.88% of body mass (0.19µl water gained) in L. venusta.” (Opell, 2021, https://doi.org/10.1636/JoA-S-19-066).
But every little bit helps.
Marbled Orb Weaver Spider Notes
- Marbled Orb Weaver Spiders live throughout North Carolina and are fairly common sights.
- Look for individual orb weaver spiders in coniferous and deciduous forests and in wet or humid areas.
- These spiders build their large orb webs in low bushes, tall grass, and under low tree branches.
- Marbled Orb Weaver spiders are mostly nocturnal; during the day, they hide from predators in leaf shelters unless they sense prey or damage to their webs.
- To make their leaf shelters, the spiders fold the leaves over and anchor the edges with silk to form tents. The spiders then hunker down and wait for prey to strike their webs.
- An easy way to find Marbled Orb Weavers during the day is to first spot one of their webs, then search the foliage near the points at which the web’s guy lines anchor to the vegetation for folded leaves. Chances are good that a Marbled Orb Weaver crouches in the shelter of the tent close to its web.
- To make their leaf shelters, the spiders fold the leaves over and anchor the edges with silk to form tents. The spiders then hunker down and wait for prey to strike their webs.
- Marbled Orb Weaver spiders are most abundant in late summer and early fall. Some large adults can even survive into November in North Carolina (Gaddy 2009).
Marbled Orb Weaver Spider Classification
- Marbled Orb Weaver Spiders are also called “Halloween Spiders”, probably because large orange females become more active and thus noticeable in the fall as they prepare to lay their eggs.
- They are also called “Pumpkin Spiders”, both because they are active in the fall when pumpkins are ready to harvest and because of their conspicuous, round, orange, or yellow abdomens.
|
Phylum |
Arthropoda |
|
Class |
Arachnida |
|
Order |
Araneae |
|
Family |
Araneidae (Orbweaver spiders) |
|
Genus |
Araneus |
|
Species |
A. marmoreus |
Binomial Name |
Araneus marmoreus |
