Underside of Calaenia excavata (Bird Dropping Spider)
The female Calaenia excavata's body grows up to 12mm, while the tiny male is only 3mm. Unfortunately, I did not find the male (it is possible he became a meal after mating), but of course it could be easily overlooked.
Despite checking the egg sacs most days, I did not see the spiderlings emerge and disperse. I did, however, break open an empty egg sac to inspect the interior. A tiny escape hole was evident.
These odd, yet remarkable little spiders are not considered dangerous. I look forward to finding more living and breeding in my garden. They are apparently commonly found in citrus orchards, so if you have a couple of citrus trees in your backyard, you have more chance of finding the Bird Dropping Spider than I have.