Bird-dropping (Celaenia excavata)

The Bird-dropping spider from Australia is a part of the orb-weaver family. Why such a funny name? Because they look just like a bird’s dropping! They’re big and have colors that trick others into thinking they’re just a bird’s mess. There are other spiders, like the ones in the Mastophora group, that look like this too.

Physical Description and Identification

Adults

• Size: The females are 0.47 inches (12mm) long, while the males are shorter and have a body length of not more than 0.09 inches (2.5 mm).

• Color: They have a pale white, black, and grey coloration likened to a bird’s dropping, as mentioned above.
• Other Characteristic Features: These spiders possess a large, broad triangular-shaped abdomen, which is concave along the midline. It also has long, spiny forelegs. When at rest, the legs remain folded against their body.

Eggs

The females produce about 13 egg sacs with each containing 200 eggs on average. The egg sacs look like marble-shaped brown balls, having a diameter of 0.47 inches (12 mm), held together with strong thread-like structures.

Spiderlings

The spiderlings emerging from the sacs have a pale color at the beginning that darkens as they mature.

The Web

Only the young bird-dropping spider makes circular webs. The females do not spin webs and have a different strategy of capturing their prey. They hang from a leaf upside down, waiting for the moth to come, and the moment it does, they seize it with their sturdy legs.

Are Bird-dropping Spiders Venomous?

Yes, Bird-dropping spiders have venom. They use it to catch their food. But for humans, it’s not very strong.

Can Bird-dropping Spiders Bite?

They can bite if they feel bothered. It might feel like a little pinch, but most people don’t find it too bothersome.

Ecological Importance and Behavior of Bird-dropping Spider

The Bird-dropping Spider plays a vital role in controlling moth populations within its habitat. Its unique mimicry and behavior allow it to capture its prey efficiently, contributing to the balance of the ecosystem. It releases pheromones that imitate the female moth’s scent, luring in male moths and demonstrating a fascinating predator-prey dynamic.

Natural Predators and Prey-Predator Dynamics: Despite its clever disguise, the Bird-dropping Spider is not without natural threats. Birds and wasps are common predators, though the spider’s appearance and behavior significantly reduce the risk of predation.

Relationship with Humans: Humans typically find this spider in forests, wetlands, woodlands, and even in orchards and gardens. Its presence is generally beneficial as it helps control moth populations. The spider’s unique appearance and behavior also make it a subject of interest, contributing to biodiversity awareness and education.

Quick Facts

Did You Know

• The markings on their body often look like a skull, giving them the name Death’s Head Spider. On the other hand, many call them Orchard Spiders as they are spotted on fruit trees waiting for their main prey, the moth.
• They follow the mimicking strategy by releasing pheromones that mimic the female moth’s odor, to get hold of their prey.

In summary, the Bird-dropping Spider is a remarkable example of nature’s ingenuity. Its ability to mimic bird droppings to evade predators and attract prey is a testament to the complexity and beauty of evolutionary adaptations.