How do these spiders that have no web and hardly ever move, catch their prey?
Unlike the fast moving spider in my previous thread, this spider is quite the reverse, seldom moving at all. It is camouflaged as a bird dropping during the day to be overlooked by predators that might be tempted to eat it. However at night it will hang up side down in an exposed position with its front legs outstretched, just waiting for something to fly into them.
The Bird-dropping Spider Celaenia excavata
Now spiders with large webs often have trouble catching insects that refuse to fly into them, so how does this spider get something to literally fly into its arms? Well this bird-dropping spider does do it, and not just any insect, but a moth of a specific gender and often a particular species! It is hunting a male moth that is attracted to the pheromones the spider releases that mimic those of a female moth ready to mate. So the male moth thinking he has located a nice receptive lady, ends up in the spiders deadly grasp.
A hunting Bird-dropping Spider
The deception of this spider however does not end there, for there is another that will guarantee success and its evening meal. The male moths do not fly directly to the female, but will initially circle around her to make sure of her presence, for this purpose he has reasonably good eyesight. Now on the photo below squint your eyes and imagine it is nighttime with a shinning moon, and what do you see? A moth, with the white parts of the spider's front legs and abdomen appearing like wings and the central portion of the spider's abdomen, the moth's body; resulting in the moth willingly flying into her waiting arms.
Squint your eyes to see the moth
Although this bird-dropping spider may not look much, it has evolved three highly sophisticated means of not only deceiving predators but successfully attracting prey.
This specific Bird-dropping Spider, Celaenia excavata, is one of the larger bird-dropping spiders with the females growing to around 15 mm (excluding legs), but like their predators, people too seldom notice them, although they may spot her egg sacs. These are spherical and almost as large as the spider herself, which she attaches to strong silken threads. The male spider is only a quarter the size of the female and is seldom, if ever seen.
Looking after her egg-sacs
Bird-dropping Spider, Celaenia excavata
Celaenia excavata is a widespread Australian (more common in Eastern States) and New Zealand species, but has taken to citrus and fruit orchards as a preferred habitat. It is often so common in this man-made environment that it is also known as the Orchard Spider.
The rear end