Box Elder Bugs

We just bought an old house and in the basement and on the lower outside walls of the house we have an infestation (I mean millions) of black bugs with thin, neatly drawn orange lines outlining their backs/wings. Thee bugs have narrow bodies, are about 3/4 of an inch long, and have long antennae. They fly occasionally, but mostly just crawl around, and they sit in large clusters–they pile right on top of each other. Strangely, we also have lots of lady bugs mixing in with them. I live in southern York county, PA (on the PA/MD line) and we have had an unusually warm winter.
Any idea what the black bugs are, why they and the lady
bugs are here, whether they are doing damage and what I can
do to get rid of them and prevent them from returning?
Many, many thanks.

Does this look familiar?

Dear Tricia,
Ladybugs are famous for communal hibernation, generally in mountainous areas. In recent years though, throughout the Eastern states, they have begun to invade homes. My internet search turned up this quote from the site :

"People first started reporting large aggregations of lady beetles (ladybugs) on homes and buildings in Kentucky during the fall of 1993. Ladybugs are normally considered beneficial insects because they feed outdoors on aphids and other harmful plant pests. However, these beetles are congregating on the sides of buildings, and if given the opportunity, moving
inside. Lady beetles do not sting or carry diseases, nor do they infest food, clothing, or wood. Nonetheless, this particular species (Harmonia axyridis) can become a nuisance when large numbers begin crawling on windows, walls, light fixtures, and other indoor surfaces. When disturbed, they also secrete a foul-smelling orange-colored fluid that can spot and stain walls, carpeting, and other surfaces….
Because the Asian lady beetle is a tree-dwelling insect, homes and buildings in forested areas are especially prone to infestation. Suburban and landscaped industrial settings adjacent to wooded areas have also had large lady beetle aggregations. Once the beetles land on the sunny side of the
building, they attempt to locate cracks and other dark openings for hibernation sites. These locations may ultimately be on any side of the structure. Common overwintering sites include cracks and crevices around window and door frames, porches, garages and outbuildings, beneath exterior siding and roof shingles, and within wall voids, attics, and soffits. Structures in poor repair or with many cracks and openings are especially vulnerable to problems."

The site goes on to recomment removing the ladybugs with a vacuum cleaner. Your other insect is most probably a box elder bug (Leptocoris trivittatus).
On it says, "When present in large enough numbers Box Elder Bugs can do damage to Manitoba Maple trees. Most people call us in the fall because they are curious about the large numbers on the walls of their houses or concerned about the numbers that are getting in the houses. Washing them off the walls of the house with a blast of cold water from a hose may help. The only way to ensure that they do not get inside the house is to fill in all
cracks where they could be getting in, a rather daunting and expensive task."
Though each of these insects is known to form communes, I have never heard of them bedding down together, but they’re not the strangest bedfellows I’ve encountered by far.

daniel, you are my hero. Many thanks for your help. We’re promptly getting out the hose and starting to fill in cracks–and I’m sleeping much better knowing that neither bug is eating my house into sawdust. What a valuable service you perform for those of us who are bug-clueless!
Many thanks again.

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