By Sam Wasson
Updated Dec 9, 2022
Pests are a common problem that plagues homeowners, especially in the summer and winter when invasive insects become more active. During these times, you might notice infestations of small, black insects gathering around your windowsills and doorframes. No matter how often you vacuum up these piles of dead bugs, they’re back cluttering up your windows in just a week or so. These bothersome bugs are unsightly and, depending on the species, pose a threat to your home or possessions.
Insects are attracted to windows because they provide several things needed to survive. First, the space around your window is warm. As the sun shines through the window, it heats the window stool (the small wooden board below the sill). Cold temperatures slow insects, making movement and activity difficult, especially during nighttime. As a result, many bugs will look for warmer surfaces (like window stools) to nest on while they sleep. Next is moisture; when the warm air inside your home comes into contact with the cool glass of the windowpane, it creates condensation. Most insects require warm, moist environments to survive, and since your windows provide both, it’s only natural that bugs are drawn to them.
There is no single bug that congregates on windows. In reality, the bugs you’re noticing could be any number of common insects prone to overwintering during the fall and winter months. Here is a list of the most common windowsill-sitting offenders.
Carpet beetles, or by their scientific name Anthrenus verbasci, are small (one-sixteenth of an inch), round insects that commonly infest homes. They have dark brown or black bodies with mottled splotches of red, pale, or orange coloration. These pests consume natural fibers like silk, wool, cotton, fur, leather, and feathers. They’re known for infesting homes in the fall and winter and causing significant damage to carpets and clothing.
Booklice, also known as barklice, or barkflies, is a pest famous for destroying books. These insects are not actually lice; instead, they’re psocids within the order Paraneoptera alongside thrips and Hemiptera (aphids and cicadas.) Unlike true lice, which are external parasites that use other creatures as a food source, psocids consume decaying plant matter and mold. Some species of barklice, specifically Liposcelis spp., often find their way indoors, feeding on paper products, grains, houseplants, or molds. Booklice are often found congregating around bookshelves or areas prone to moisture, like windowsills.
These pests are extremely small, only measuring up to three-sixteenths of an inch, and have a brown or pale appearance. It can be hard to notice booklice in small numbers due to their minuscule size, but in swarms, they can appear as swaths of small, black-brown specs.
Out of the insects on this list, clover mites are easily the smallest, only measuring up to one-thirtieth of an inch in length. Clover mites, or by their scientific name Bryobia praetiosa Koch, are one of the most common garden-infesting pests. They chow down on plant matter, creating thin, white cross-hatched lines across leaves and flowers. While a problem in the garden, clover mites are also known to migrate indoors once the weather turns cold or if there is a massive influx of rain.
Clover mites typically have a minimal impact on lawns and gardens but can be a pain to deal with when they become unwanted house guests. Clover mites are considered a nuisance pest, as they don’t bite, carry diseases, damage home structures, or feed on carpets, clothing, or stored goods. The problem arises when these pesky pests are crushed, leaving notable red splotches or streaks behind. These marks resemble blood but are, in reality, a mixture of pigment and body fluids. As a result, these mites are often confused with bed bugs or fleas, often causing a scare to homeowners.
The Asiatic garden beetle, or Maladera castanea, is originally from Japan and was first discovered in the U.S. in New Jersey in 1932. They lay their eggs in the fall, growing to larvae in the early spring (damaging grass root systems all the while), then emerge in early summer to feed on plant matter. They can cause significant damage to lawns, gardens, and ornamental plants in large numbers. They’re found across the entirety of the United States but are most prevalent in the Northeastern portions of the U.S. These bugs are about a quarter of an inch in length, bean-shaped, and have a rust-brown or golden-brown carapace.
After they lay eggs, they’ll search for warm places to overwinter and consider your house a great place to hide away. Once indoors, they’ll look for moist, warm places with plant matter to settle down; as such, they’ll quickly be drawn to windowsills or potted plants.
The biscuit beetle, drugstore beetle, or Stegobium paniceum is a stored-product pest that commonly infects granaries, warehouses, and households worldwide. Famous for eating a wide variety of products, such as rice and cereals, it’s a serious economic and agricultural pest.
In American households, they pose a problem in the home, lawn, and garden. Their larvae will damage the roots of grasses, while the adults will quickly damage fruits, vegetables, and ornamental plants. Like many other beetle species, these pests overwinter during the fall and prefer warm locations like sheds, basements, attics, closets, and pantries. Like weevils and other pantry pests, they can hide and reproduce inside dry goods. We recommend investing in sealable airtight containers to prevent pantry pest infestations. They’re about one-seventh of an inch long, with cylindrical bodies, segmented antennae, and dark brown to black coloration.
Keeping pests out of your home can be difficult. Insects often find their way indoors through small crevices and openings in your foundation, siding, doorjambs, window frames, or through gaps in screens. Some pests, like fleas, cockroaches, and mites, act as unwanted passengers, hitching a ride on other household members. The best way to keep these unwanted guests away from your home is to:
Unfortunately, there is no shortage of pests that love to sneak indoors, especially once the seasons change and temperatures drop. While many are harmless, some can threaten your home or possessions. One commonality between these home invaders is that they love moisture and heat. So your best way to keep them at bay is to deprive windows of excess moisture. While this can be difficult, we recommend frequently checking your windows’ weather stripping and replacing it if necessary. By keeping your weather stripping in good condition, you not only create an additional barrier for bugs to get through but also keep water from getting in.
If you’re experiencing an abnormally large amount of these pests, you should contact a pest control company. A professional exterminator can assess your situation, classify the type of insect you’re dealing with, get rid of them, and help you prevent future incursions. Furthermore, while the critters on this list are the most common types of pests that gather around windows, others can pose an even greater risk, like carpenter ants or termites. When dealing with these pests, pest control companies can be invaluable in preventing serious damage.
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