I can't answer your leafdrop question, but I can tell you this is a Ficus microcarpa, and a lovely one, too. It's definitely getting enough light; their leaves go pointy in too much shade. If you don't see any evidence of bugs, the leafdrop may be either a temperature change reaction or something to do with the potting mix it's in. Hopefully others can speak to that.

At some point should it not be expected to loose some leaves? Perhaps seasonally?

See images of the mature tree at: UFEI - SelecTree: A Tree Selection Guide - Ficus microcarpa

I believe a lot of indoor ficus (definitely benjamina, but possibly microcarpa as well) are prone to leaf drop when light levels go down. If it is otherwise appearing happy, this may well be the problem. You could add a plant light hung above it and set to be 12on/12off, or you could let it get a bit 'naked' inside the canopy and then prune it back when it starts to grow actively in the spring, combined with fertilizing it.

Alternative problem may be too low humidity - if it's not the light levels, have you turned your heating on? Turning on heating drops relative humidity indoors down very severely, and that can also cause plants to drop leaves, especially the older ones (which would naturally be inside the canopy).

I would suspect the light foremost, but it could be humidity, or a combination of both.

Thank you, everyone! You've been very helpful.

I think the tree looks better in the pictures than in person. It has lost a lot of leaves in the inner canopy, but as I say, the outside canopy seems to be compensating. I also forgot to mention that many of the leaves are curling, which is an issue that preceded the leaf drop. Does anyone know, will the inner canopy fill back in next spring when light levels change again? Is there anything I can do at that time to encourage that growth?

I also sometimes wonder if it's rootbound, perhaps I should repot it in the spring. It's about 4 1/2 feet tall from the floor and in a 10" pot.

Thanks again, folks!

That's look like ficus microcarpa ginseng, or also known as microcarpa long Island. The leaves thick and lil rounded on the tips. In tropic, people graft this ficus on benjamina trunk because this ficus isn't easy on falling it's leaves. So if this ficus falling it's leaves, maybe there's something wrong with the root part. This ficus have caudex root, like a ginseng. Sometimes so big that taking up a lot of space in pot. Try dig a little. If there's a huge caudex root, lift it up and add extra soil to make room for smaller roots to expand.

Yes, unless you're in far south Florida or Texas, you'll want to wait until spring to do a full repot. That point will also be a good time to prune the growing tips to induce back-budding (where the leaves fill in the inner portions of the branch). There are many great posts on how to do this. I think Al's (Tapla's) Ficus Trees in Containers Part IV is the most extensive.

As for the leaves curling downward, that's a thing ficuses do when they're trying to shed excess water. You're probably overwatering, most people do at first. Forget watering by the calendar and go by what the plant actually needs: get some bamboo BBQ skewers & use them as dowels to measure how dry the tree is. Insert one into the pot as far as it will go, and don't water until the stick comes out dry all the way down.

You'll want to get the tree into a better draining mix in the spring, but it's really late in the year for that, excepting subtropical areas, and it should be okay until then.

If you were to decide the plant was loosing leaves over being root bound than that would warrant repotting. If not, I never repot sick plants. The feeling is you end up with a sick plant that is now in shock with root injury too. It have killed plants I was trying so hard to save, by doing to much and only adding it it's problems. It's so hard to just observe.

Update:

I found these dead little guys in the saucer. Does anyone know what they are? I haven't seen any creepy crawlies on the leaves, although I haven't looked with a magnifying glass. I have noticed small black dots (see second picture from original post) on many of the fallen leaves but they don't appear to be bugs.

The tree continues to loose ten or so leaves a day from its inner and lower canopy and is thinning considerably. I still think the most likely cause of the leaf drop is the change in temperature/daylight, but maybe these little larvae (?) are evidence of something else wrong. What do you folks think?

The curly ones are millipedes. They're harmless, live in leaf litter outside, and only come indoors seeking moisture. I can't tell what the other bug is at this distance. It could be an earwig or any number of beetles. Every drought season, we see millipedes, and earwigs and sowbugs for that matter, creeping inside in search of any drops of water they can find. They dry out and die pretty quickly unless you've got leaky pipes or an indoor atrium...or spiders or house geckos get them first.