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How Big Are Bed Bugs

Posted on April 1st, 2018 by Panther Pest Control Team

Last Update: 18.07.2018

bed bug picture

Image source: USDA; License type: CC BY 2.0

It’s hard to say exactly how big bed bugs are, as they need to go through 7 stages in order to complete their life cycle. In each particular stage, the bed bug changes its size, appearance and behaviour, that’s why we decided it would be best to give you a deep description of the bed bug’s size in all phases.

Bed Bug Eggs Size

The size of the bed bug is not constant as it goes through many life stages before it reaches maturity. The lifecycle of the bed bug contains 7 stages (5 of each larva) and the insect grows progressively in each of them.

  • Size of a Bed Bug Egg

    The bed bugs eggs are the first stage of the cycle and at that time it is about 1mm long. It’s white and is very distinctive. You will see many of these at the place of infestation – usually under the mattress of the bed. If you notice bed bugs there, make sure to treat the bed bugs on the mattress properly.

  • First Stage Larva Size – Nymph Phase

    During the first stage of the larva, the bed bug grows in size a little bit and reaches a length of about 1.5mm. In this phase, the bed bug isn’t sexually mature yet and the nymph needs to complete a moulting stage that may happen only after the first blood meal. In this phase, the insect is usually white or light yellow.

  • Second Stage of Bed Bug Larva

    When the insect reaches this larval stage, it grows with additional 0.5mm and becomes 2mm long. To go further, it needs to feed with blood again to complete another molt stage. The colour becomes darker than the first stage. The insect gets a red-brown body and distinctively yellow head.

  • Third Phase of the Bed Bug Life Cycle

    Without exception, the bed bugs grow exponentially with additional 0.5mm and become 2.5mm long. It still needs another blood meal for the next molt stage and doesn’t change its appearance significantly.

  • Size of Bed Bugs at Fourth Stage

    During this phase, the bed bugs become a little darker and its colour is red-brown. It reaches a length of 3mm and takes another blood meal for the penultimate moult phase. Luckily to everyone, professional pest treatments can take care of bed bugs in all of their life stages.

  • Fifth Larva Stage

    This is the last larval stage of the bed bug and it’s also the phase during which the bed bug goes through the molt stage for the last time. At this time the bed bug increases its size significantly with about 1.5mm and becomes 4.5mm long. This growth is 3 times higher than in the previous stages.

    The bed bug’s body shape also alters a little bit and the back of the insect becomes wider.

  • Adult Bed Bug – Last Stage of the Life Cycle

    This is the 7th and final phase of the bed bug’s life cycle. It’s the time when the bed bugs reach its limits in terms of size and maturity. It becomes about 5.5mm long and is now able to take repeated meals instead of just one. There aren’t any molt stages at this time.

    The adult female bed bug is able to lay up to 5 eggs each day and this repeats until the end of the bed bug’s life cycle. This makes this insect able to multiply really fast. That’s why it’s reasonably to exterminate them immediately when you spot the bugs. If you can’t deal on your own, don’t hesitate to seek help for professional bed bug extermination.

    When completely fed, the bed bug changes its form slightly. It becomes a little longer and thinner. If you notice any of these, it means they’ve just finished feeding and best to not be smashed as it this will leave a blood spot on your sheet, mattress or furniture.

What is the size of a bed bug full of blood?

How big do bed bugs get, you probably wonder, don’t you? When completely grown, adult bed bugs can reach a size of about 5.5mm long. While feeding with blood their diameter grows mostly in length. This means that right after the feast a bed bug can significantly increase the size of its diameter and becomes about 6mm long.

The crawling insect needs roughly 3-10 minutes to become fed up with its victim’s blood, often leaving a severe rash and itchy bite marks after that.

How Big Are Bed Bugs Compared to Fleas

how big is a bed bug compared to flea - bed bug picture

Images sources: Wikipedia; Wikimedia;
License type: CC BY-SA 3.0; CC BY-SA 4.0

Fleas are significantly smaller than the bed bugs but this can hardly be seen with naked eye. The average size of an adult flea is 3mm which is about 2 times smaller than the average adult bed bug (5.5mm – 6mm).

Both bed bugs and fleas can cause severe problems to humans such as:

  • Itchy bites;
  • Raches;
  • Psychological effects.

While bed bugs prefer to bite humans and rarely animals, it’s exactly the opposite for fleas – they prefer to attack animals and bite humans pretty occasionally.

Read more about differences between fleas and bed bugs.

How Big Are Bed Bugs Compared to Ticks

how big are bed bugs compared to ticks

The only similarities bed bugs and ticks have are the following:

  • Both are flat:
  • Wingless
  • They bite people;
  • Feed on people’s blood.

Now the differences. While bed bugs are insects, having 6 legs, ticks are arachnids (an adult tick has 8 legs) such as the spiders.

While in unfed condition, adult female black-legged ticks (red and brown coloured) are approximately from 3 to 5mm long. After being engorged with blood meal, female ticks change not only their size (about 10mm long) but also their colour appears darker.

Adult males are smaller than females and are uniformly brown in colour. Nymphs are between 1-2 mm long, also eight-legged and larvae are less than 1 mm long (about poppy seed sized) and have only 6 legs.

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