How to Identify a
Bed Bug Infestation
Dini M. Miller, Ph.D., Department of Entomology, Virginia Tech
Introduction
You cannot just “get” bed bugs. They have to be brought into your home. So what is your first clue that you
have brought bed bugs home in your luggage after a trip, or on a piece of used furniture that you bought at a garage
sale? Most people become suspicious of a bed
bug infestation when they find unexplained
bites on their bodies. Most commonly a per-
son will go to bed feeling fine but wake up in
the morning with itching bites. While bites
might suggest bed bugs, they are not a good
method for diagnosing a bed bug infestation.
This is because bite reactions are so variable
from person to person. For instance, a person
who has been bitten while traveling may not
react for several days, and only notice the bites
after they have returned home. These bites do
not mean the home is infested. Alternatively,
a person may not react to bed bug bites at all.
This can allow an infestation to get started in
their home and remain unnoticed until the
bed bug population increases so much that
bed bugs start to be seen. Because bites are an unreliable indicator of an infestation (they may not be bed bug bites
at all), it is very important to be familiar with the other signs that bed bugs leave behind to detect a real infestation
(particularly a small one). By looking for specific bed bug evidence, the infestation can be identified early before the
population becomes difficult to control.
Bed Bug Identification
It is very important to know what bed bugs look
like. The adults can easily be seen with the naked eye.
Adult bed bugs are reddish brown in color, wingless,
and are about the size of an apple seed. Immature bed
bugs (there are 5 immature or nymphal instar stages)
can also be seen with the naked eye but they are smaller
than adults, and translucent whitish-yellow in color.
The most difficult life stage to see is the first instar
nymph. This is the youngest life stage that hatches out
of the egg. These nymphs are so small that they are difficult
to see unless they are moving or have recently fed (bright
red when full of blood). Bed bug eggs are also tiny,
about the size of the head of a pin. The eggs are a pearl-
white color and have obvious eyespots if they are older
than 5 days.
Bed bugs can look somewhat different depending on
their feeding status. If an adult bed bug has not fed recently,
it is approximately
3
⁄16" long and oval in shape. In fact, an
unfed bed bug can look like a flat disc. However, once it
takes a blood meal the body blows up like a balloon. The
bed bug elongates so that it looks more like a torpedo than
a disc. The color also will be a bright red if the bed bug has
fed within the last couple of hours. The bed bug will darken
and flatten again over the next couple of days as it digests
the blood meal.
Bed bug nymphs also change in their appearance after a
blood meal. A hungry bed bug nymph is almost completely
pale white or yellowish. However, once it is fed it plumps
up, becomes brilliant red, and looks like a plump raspberry
seed. Nymphs are the easiest to see when they have
recently eaten.
Identifying Molted Skins
Immature bed bugs have to take a blood meal in order to grow, and molt to the next life stage. The molting
process is where the bed bug has to shed its “skin.” Because all insects (like the bed bug) have their skeleton on the
outside of their body (exoskeleton), they have to shed it in order to grow larger in size. Because each bed bug has five
immature stages before it becomes an adult, it will have to molt (shed) five times. After adulthood, the bed bug no
longer grows or sheds its skin. In a large infestation there will be many thousands of these molted skins lying around
where they bed bugs have left them behind. In a new infestation, say in a hotel room, bed bug evidence may be very
hard to find. Yet, because the largest percentage of any bed bug population is always in an immature stage, there is
always potential to find these cast skins.
The molted skins of the bed bug look very similar to the bed bug itself. They are the same shape and generally
translucent in color. However, you will notice that they look like an empty bed bug shell. They will be different sizes
depending on the life stage of the bed bug that molted. In small infestations, molted skins can be found almost any-
where. In large infestations, most are found in areas where bed bugs aggregate together in groups.
Where to look for molted bed bug skins:
• Along mattress seams
• Behind head boards
• In ceiling/wall junctions
• Along baseboards
• Stuck to personal belongings
Identifying Fecal Spots
Bed bugs feed every 5-7 days if a host is present. On the days they are not feeding, they are spend their time di-
gesting their previous meal. Blood contains a lot of water so the bed bugs must condense their meal right away and
excrete some of the excess liquid as waste. This digested blood is then deposited wherever the bed bugs happen to go
after feeding. The excreted waste comes out in a semi-liquid from and can be easily seen on the surfaces of mattresses,
bed frames and other locations where the bed bugs travel or aggregate. These fecal spots are black in color (not red
because the blood has already been digested) and are often seen in groups of 10 or more. However, if the infestation
is low, and the bed bug was just passing through the area, there may be only one of two spots in a particular location.
Fecal spots can be found anywhere in a large infestation, but when the infestation is small, there are some places
where fecal spots are more likely to be found. See below.
Where to look for Fecal Spots:
• Along the mattress seams and on the tag
• On the wood frame of the box springs
• Behind the head board
• Along the tops of baseboards or the edge
• of carpeting
• Ceiling/wall junctions and behind pictures
• on the wall
• At electrical outlets
• In curtain seams where they gather at the rod
Notice that the bed bugfecal spotting can look similar to German cockroach feces that you might find in
an apartment with a heavy cockroach infestation. One way to tell these two types of fecal spots apart is to first
look for additional bed bug evidence in the area. Do you see shed skins or hatched eggs? If not, touch the fecal
spots (yes, touch them). Bed bug fecal spots have a smooth feel because they consist of a dried liquid food
(blood). German cockroach feces tend to feel very granular because they contain solid wastes.
Identifying Bed Bug Aggregations
Looking for bed bug aggregations is similar to looking for
fecal spots in that bed bugs often leave numerous fecal spots
where they aggregate together after feeding. However, these
aggregations also contain a variety of other bed bug evidence:
• Live bed bugs (multiple life stages)
• Fecal spots
• Cast skins (from nymphs that have molted)
• Live and hatched eggs
Although the photograph above makes a bed bug aggre-
gation look obvious, these aggregations are not so easily identified if you do not look closely. For example, take a look
at the photograph taken of an apartment ceiling on the next page. At first glance, this lookes like mold or mildew
problem, indicative of a moisture issue coming from the apartment upstairs. However, if you look more closely you
can see that the “mold” is actually numerous aggregations of bed bugs on the ceiling. The black material is the fecal
spotting described previously.
Where to look for bed bug
aggregations:
• Along mattress seams, in the tufts
• and under the mattress tags
• Behind the headboard
• Inside the holes for set-in screws
• Along wood creases in the box
• springs or in bed frames
• Where the box springs fabric is
• stapled to the wood frame
• Behind loose wallpaper
• Behind chipped paint
• Under the base of the air conditioner
• Beneath the wood framing that holds the bar in the closet
• Along the interior frame of closet doors
• Behind baseboards
• Inside the baseboard heaters
• Inside curtain rods, and on the curtains near the top where they are pleated
• In personal belongings, including books, stuffed animals, picture frames and hundreds of
• other locations
Summary
The first clue suggesting that you may have a bed bug infestation is often the presence of itching bites. However,
bites reactions are quite variable and may not be due to bed bugs at all. Be aware of the other signs that bed bugs
leave behind: fecal spots, molted skins, and aggregations.
