do you need a microscope to see bedbugs

How Small CAN Bed Bugs Be?

Bed bugs are small, but are they invisible? It appears so because most of us will not see a bed bug in our lifetime. That’s why we’re covering in this article bed bug anatomy, comparing their sizes to day-to-day measures and showing you how small they can be. How small is a bed bug egg? Are bed bugs nymphs visible to the naked eye? How large do they grow? Would you need a microscope to see them?

Bed bug sizes and proportions

Most of us can see bed bugs without a magnification glass, at least if we have good eyesight. These pests avoid detection and know when to leave their nests, but they are large enough for us to notice them.

The size of a bed bug is variable depending on the life cycle. Bed bug females lay 5 eggs every single day, and these eggs are relatively small. When bed bugs hatch, they start as small nymphs, too. These nymphs are translucent and can be difficult to see, mainly because they are a pinhead size. After feeding, they gain some color, and we can see them more clearly.

Then, each nymph undergoes a series of transformations until they become an adult bed bug. When they reach adulthood, bed bugs do not grow any longer. The only way to change their adult size is by eating because they store blood in the body, and it takes extra space, making them more noticeable and expanding their bodies in the process.

But what is the measure of bed bugs in the different stages of their development?

Bed bug eggs are tiny and translucent. They are difficult to spot because they are 1 mm or less. When they hatch, a bed bug nymph in its first stage measures the same as the egg (1 mm) or a bit more when fed (1.5mm). Then, bed bugs get into their second stage of nymph life, in which they are a bit larger (no more than 2 mm). During the third stage of their nymph life, they increase their size to 2.5 mm and adopt the size of a sesame seed (3 mm) when they reach the fourth stage of their development. In their final stage of nymph development, they reach 4.5 mm, and adult bed bugs can be somewhere between 5 and 7 mm, depending on whether or not they are already fed.

Now, if you want to make sure that it is a bed bug what you’re seeing, consider these descriptions of an adult bed bug anatomy:

They are about the size of an apple seed, which is no less than 5 mm but no more than 7 mm. If you prefer inches, that would be 3/16 of an inch to 1/4 of an inch. They are flat, and their shape is oval when they are not fed. They adopt a rounder appearance after feeding, and their color changes from a reddish-brown into bright red. These insects produce a musty smell and do not jump. They only walk or crawl on the floor and walls. It is also important to note that bed bugs will not look for shelter in your body and probably won’t hide in your clothes. Instead, they look for dark hiding spots to stay all night long and wake up at night to crawl directly to your bed.

Why do you wake up with bite marks but never see a bed bug?

Most people have a similar problem when they are infected with bed bugs. They have never seen one but continuously wake up with bite marks. They may even think these are mosquito marks or another type of pest because otherwise, you could see them moving in your bed or your room, right? Unless they are invisible.

But as noted above, bed bugs are far from being invisible. You may not be able to see bed bug eggs because they are translucent and carefully hidden from your sight. But you can easily spot a larger nymph and do not need a magnifying glass to see a bed bug adult. If that’s the case, why do you only come across with their bite marks?

Because they evolved around humans and know precisely how our biologic cycle goes, they are nocturnal creatures and won’t leave their hiding places during the day. They wait for the night when everything is dark, and people are likely deep asleep. Only then would they crawl out of their nests and join you in the bed to have a feast.

The most reliable way to spot a bed bug is either having a severe infestation in which they can no longer fit in the nest or understanding exactly where to look.

Where to find them and how to get rid of them

Bed bugs will always try to remain in their hiding places during the daytime. So, if your bed bug problem is only starting, you need to know where they are located.

Bed bugs usually look for cracks and crevasses in your furniture or walls. They can also live inside your mattress, especially when it’s old and torn. They are particularly clever and may even hide in the electric outlet or behind the wallpaper. The more clutter you have, the more hiding places you will provide to them, especially if we’re talking about your room. They always prefer to be close to where you sleep but can walk longer distances if they don’t find an appropriate hiding place next to your bed.

Looking for the nest is a critical part of getting rid of them. Next, you need to know what insecticides to use. If you have pets or small children, we recommend diatomaceous earth, which comes as a powder you need to spread in their hiding places. If you’re not worried about toxicity, you may also use insecticides that kill bed bugs instantly.

But in some cases, bed bug problems are too severe to take care of them on your own. So, if you’re having recurrent issues or can’t take care of them on your own, look for a professional pest control specialist who will assess the severity of the infestation and give you detailed recommendations on what to do next.


Reinhardt, K. (2018). Bedbug. Reaktion Books.

Potter, F., Haynes, K. F., Connelly, K., Deutsch, M., Hardebeck, E., Partin, D., & Harrison, R. (2010). The sensitivity spectrum: human reactions to bed bug bites. Pest Control Technology38(2), 70-100.

Olson, J. F., Moon, R. D., Kells, S. A., & Mesce, K. A. (2014). Morphology, ultrastructure and functional role of antennal sensilla in off-host aggregation by the bed bug, Cimex lectularius. Arthropod Structure & Development43(2), 117-122.

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