Q.What are those tiny cocoons that cling to the walls inside?
What you are describing is a caterpillar called the plaster bagworm, which is very common and generally harmless. The caterpillar lives in a gray, flattened, watermelon seed-shaped case about a half-inch long. The case is constructed of silken fiber and sand particles, lint and other debris. It has a slit-like opening at each end, which lets the larva (caterpillar) move around and feed from either end. Plaster bagworms are easily seen on light-colored walls.
Bagworms can also be found on outside walls and attached to the undersides of patio furniture, and in garages.
Plaster bagworms mainly feed on spider webs, however, they will also feed on fabrics made of natural fiber such as silk. Usually bagworms don’t damage anything indoors unless you allow them to crawl onto fabric. Since they move very slowly, it is easy to keep them away from clothing. If you find some on your indoor walls, check your closets and dressers for this insect and remove any you find.
They enter homes through crevices around doors and poorly sealed windows.
To control the plaster bagworms indoors, good housekeeping is important, especially regularly removing spider webs. Vacuum or sweep down and remove any spider webs and bagworm cases. Insecticides do not control this insect. Place weather-stripping around doorways, especially over the threshold and sliding glass window tracks to keep them from entering your home.
Bagworms on exterior walls cause no damage but can be swept or picked off and disposed. It is much better to sweep spider silk off walls since power washing them may damage paint or stucco.
Send undamaged (live or dead) insects in a crush-proof container such as a pill bottle or film canister with the top taped on. Mail them in a padded envelope or box with a brief note explaining where you found the insects.
Do not tape insects to paper or place them loose in envelopes. Insect fragments or crushed insect samples are almost impossible to identify.
Send them to the address of your county extension office, found in the blue pages in the phone book under county government.