Hi

This is not a caterpillar but a millipede.  It can live up to seven years in the organic matter in woods and in mulch. As numbers increase and organic matter becomes scarce or dry weather sets in  (not likely this year) they tend to migrate to find new feeding areas. They prefer moist, humid areas so your home and cracks in pavement may be a place for them to temporarily reside until better conditions allow them to move on.Control Measures
Millipedes, related to lobsters, crayfish, and shrimp,
require moist habitats and areas of high humidity. It is
important to keep the house and outside area as dry as
possible. OSU  has a factsheet  2067A published in 2010, access by going to our website <personal data hidden>. In the next couple paragraphs are excerpts of the factsheet :
"Prevention
Millipedes prefer moist, decaying organic matter
(similar to forest soil) and shade. Always keep compost
piles, grass clippings, rotting wood, leaf piles, plant debris,
stones, etc., away from the house foundation as far as
practical to reduce moist, damp, dark places where feeding
and reproduction can occur. Be sure to check for wood
imbedded or buried in the soil.
Also, ivy beds and mulch near the house may become
a favored habitat. Rake and remove trash or leaf litter in
a strip three feet wide surrounding the house foundation
if practical, exposing the soil surface to drying from the
air and sunlight. Repair and seal cracks and openings
in the foundation wall and around door and window
frames with caulking compound, weather stripping, or
door sweeps.
Properly ventilate basements and subfloor crawl spaces
to eliminate excess moisture. Indoors, many will die of
desiccation (drying out) and can be collected by broom
and dustpan, vacuum cleaner, or other mechanical means
and discarded.
Insecticides
Total control of millipedes during migration periods
is difficult. But several insecticides are registered for
“perimeter” treatments. The concept is to apply a barrier of
insecticide that will either repel or kill the millipedes that
try to cross the barrier. Both liquid sprays and granular
formulations are available at most garden centers. These
products should list millipedes on the label as not all
insecticides are able to control these non-insect arthropods.
Retreatments are commonly needed though some
products claim to provide season-long control.
Sprays, fogs, and total-release insecticides (commonly
called bug-bombs) are not effective in preventing millipedes
from entering a home or building. At best, these
may kill any active millipedes, but most of these products
have no long-lasting residual effects"
 

Thank you. I found the fact sheet and will take action.