These are specimens of a type of tenebrionid larvae (mealworm-like larvae, that turn into darkling beetles) found within homes.
The first set is from Mountain Ranch, CA. 25 August 2015. Specimens collected by Trevor Cuthill. Specimens were in various locations throughout the house, but most prevalent along the baseboard of the exterior wall in the living room.
Second set is from a home in Valley Springs, in a shop area. Specimens collected by Ryder Richards, 20 July 2016. Ryder reports the room had lots of sawdust.
Third set are photos of the adult beetles, collected by Ryder Richards from a Valley Springs job site.
Thanks to Dr. Lynn Kimsey for confirmation of the ID.
In our cases, within these homes, we have not found what these larvae are eating. Our best guess is that these are lesser mealworms. We are still looking to find the food source for them.
Click on an image to enlarge it.
Mealworm larvae from within a house
Second set. Valley Springs, July 2016.