[SWAMPSNIPER]

I was in pest control back in the 70s. I worked commercial kitchens at night when they were closed. I would treat with a residual pesticide, then use an aerosol flushing spray. More than once I've used a shovel to pick up dead roaches. When the spray started spreading the damned things would boil out all over the place.

Hollow block walls are roach motels.

[djf]

I've read that at least in the bug world, roaches are relatively clean. If you watch them close you will see them grooming themselves often.

One of the worst, if not the worst, is the common fly. They are very hairy little beasties naturally attracted to decaying material which is what maggots need.