How might a cob evolve?

Question

The cob is a small, terrestrial invertebrate that is found almost exclusively in undisturbed places, mostly abandoned buildings. They can eat almost anything, but their diet consists mostly of dead bugs and plant life in nature, or old food in buildings. Their most notable characteristic is that they create dust at a high rate, which, due to the fact that they live in uninhabited areas, settles down into a thick layer. What could the cob have evolved from, and why would it evolve this way?

Answer 1

Cob = Roach

found almost exclusively in undisturbed places

Some species of roach prefer undisturbed places, since places that are disturbed frequently are places where a predator or human is more likely to find them and kill them.

So, check.

mostly abandoned buildings.

Number one reason I don't hang around abandoned buildings, more than the collapsing hazards, rats and hobos is roaches.

I think we can say check.

They can eat almost anything, but their diet consists mostly of dead bugs and plant life in nature or old food in buildings.

This is what roaches eat in the wild. Check.

Their most notable characteristic is that they create dust at a high rate, which, due to the fact that they live in uninhabited areas, settles down into a thick layer.

Roaches shed a lot:

Shed skin - Look for this evidence in locations you suspect they are sheltering. Cockroaches shed nymphal skins 5-8 times as they mature to adulthood.

They reproduce really fast, and with each individual shedding like that, all it takes is for the shedding to produce fragile skins that crumble into dust easily. This might already be the case in the real world - a lot of dust in inhabited homes comes from human skin, nails and hair disintegrating as far as I remember.

Given time, all that shed roach skin may settle as a layer of dust. Therefore, check.

---

Now that we have established the roachness of the cob, all it takes for cobs to exist are the same evolutionary pressures that led to the roach. Every ecosystem has its set of recyclers and the roach is one of them. Usually the smallest carrion eaters evolve to reproduce fast (leading to spawning in large numbers, leading to more shedding, leading to more dust!) and eat anything. Consider that just as there are roaches on land, there are shrimps in the sea fulfilling the same role.