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I was observing this spider (caught in a Petri dish) under my microscope, when I noticed that a small, round object emerged from its rear end. It appeared to be black and white in appearance. I am guessing that it is an egg, but I am not sure whether it is one or not. The diameter of the object is approximately 300µm.

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The spider seems to resemble Hasarius adansoni from photos:

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The scale bars in the image are 5mm in length. The spider and the object are imaged together in the frame for scale.

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Can anyone conclusively identify the spider and the object? The photo was taken in Singapore in November (although the seasons don't really matter in Singapore).

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    $\begingroup$ Excellent images. I wish I could say anything conclusively other than, 'wait and see.' Maybe you'll get lucky and the answer will present itself conclusively. $\endgroup$ – johntreml Nov 3 '15 at 15:24
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I do not know what species of spider this is, but I think the white ball is actually spider poop. Unfortunately a quick search did not return many references, but here is a picture for comparison.

Spider Poop

Spiders produce uric acid, which is a near-solid and excreted out white. This is done to minimize water loss. These malpighian tubules drain into an pouch attached to the digestive tract, or stercoral pocket. The uric acid waste from the is combined and eliminated together with solid waste from the digestive tract. In your spiders case, this would be undigested insect parts (black) mixed with the uric acid (white).

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    $\begingroup$ Actually, I forgot to update this question, but after 3 days the unknown object was found to be liquefied into a spread around 3mm in diameter. This supports the hypothesis that the ball is spider waste. $\endgroup$ – March Ho Jul 31 '16 at 23:36

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