The insect is about 5mm in length.ovoid shape shield/shell.sometimes the worm head will appear out of its shield like how a tortoise does and when you are nearby it,it hides itself within the shield again.the shell is usually greyish white,sometimes darker in colour.please help.
This is called a plaster bagworm and is a type of clothes moth. The larva lives inside the sac that it makes from bits of fabric. They can damage natural fibres (silk, wool) but are otherwise harmless. See http://www.livingwithbugs.com/clothes_moth.html for general information about clothes moths.
I can answer questions in any area of entomology (study of insects, spiders, mites, ticks, and other terrestrial arthropods). Contact me about home and garden insects, insects that bite and sting, and insects that damage homes such as carpenter ants and termites.
20 years as university extension entomologist, now retired; currently publish a website about home and garden insects.
Publications see www.livingwithbugs.com/resume.html