This insect is a western conifer seed bug (WCSB), a type of leaf-footed bug. It is related to (and closely resembles) another plant bug known as the squash bug. Both have a 5-sided shield behind the head, which is characteristic of most true bugs of the Hemiptera group. One distinct difference between the WCSB and the squash bug is that the WCSB has a leaf-like enlargement on its hind legs.
Where did it come from and why is it in my house?
As with most insects, you probably didn't even notice this particular insect during the summer. But it was out there, discreetly feeding on green cones and needles of pine and Douglas fir. Then, with the onset of cold weather, WCSB went in search of a protected site where it might spend the winter. (Quite often such protected sites are people's homes.) Because these insects end up in homes, garages, etc. accidentally, we call them "accidental invaders." Other examples of accidental invaders include lady beetles, boxelder bugs, and cluster flies. These insects eventually find their way inside homes by crawling through cracks and crevices on the outside of buildings, e.g. around widows, doors, and under siding.
Is it harmful?
No. They are very specialized feeders and will NOT feed on anything other than pinecones and pine needles. They will not feed on food items or plants. They will NOT bite you or your pets. In fact, once "trapped" inside your home, they will eventually starve and die.
What can I do to get rid of it?
Fortunately, people do not usually see more than just a few western conifer seed bugs at a time and they can simply be swept or vacuumed up. The best way to prevent (or at least greatly minimize) future "accidental invader" problems, is to caulk and seal any exterior cracks and crevices, mainly around windows, doors, and under siding.
