The bird dropping spider (Celaenia excavata) derives its name from mimicking bird droppings to avoid predators, mainly birds. However, there are other species of spider that resemble bird droppings, for example species of Mastophora (a bolas spider). The males are much smaller than the females, about 2.5 mm as opposed to 12 mm.
The females have up to 13 egg sacs, with about 200 eggs each, strung together with strong threads. Their toxicity is unknown, but may be able to cause mild illness in humans. The bird dropping spider stays motionless on its web during the day, only hunting for prey at night. It hangs down from a single silk thread and releases a pheromone which mimics the sex smells released by female moths. When a moth comes near the spider will capture it with their powerful front legs. They can be found in Australia, mainly along the eastern and southern coasts.