Humans are omnivorous creatures. That means we can eat almost anything, but definitely not everything we come across. For example, we don’t have enzymes to digest certain types of fiber properly. And we can’t live on human blood or any kind of blood at all. It would actually kill us after a while.
However, some creatures suck on blood, including bats and mosquitoes. But here’s the most interesting part….. interestingly because many bat species do not live on blood and mosquitoes (only the females bite you) definitely don’t need blood, except for when the are laying eggs. When the female mosquito mates and needs protein to lay her eggs, that’s the only reason why she begins looking for sources of blood. Otherwise, mosquitoes would not eat blood at all because they mainly feed on honeydew and nectar in flowers and plants.
So, if that happens in the animal world, we typically associate them as bloodsuckers, what happens in the case of the Insect organism known as the bed bug? Do they have human blood as their most important meal? Or is it only a side dish or an appetizer?
What do bed bugs eat?
Bed bugs feed on blood and are different from mosquitoes; it is not an option for them. It is their primary source of energy. However, even though they prefer fresh human blood, they can also live up on your pets’ blood and other mammals.
When bed bugs are younger, they require fresh blood to evolve into an adult bed bug. In this stage, nymphs go through 5 phases, leaving an empty shell between one another, and requiring a blood meal to complete each step. They do so every week or so.
After this time, when they become adults, bed bugs continue feeding up on human blood and any other source they come across. Similar to younger bed bugs, they usually take a new meal every week. However, they are capable of surviving for months without a new source of fresh blood. That’s why people wonder if they are feeding something else during that period.
Are they capable of eating something else?
If you compare bed bugs to other insects, you may think they are likely eating something else, and not only blood.
One of the most common mistakes is that bed bugs eat dead human skin, like dust mites. Actually, some people mistake bed bugs for dust mites because they also live in your house. However, dead bugs cannot eat dead skin because their digestive system is not specialized to process this type of meal. They would have to chew before swallowing if they ate dead human skin, and their mouth is only made for sucking, not for chewing.
The same goes with food crumbs and other solid foods. They cannot feed on your left-outs as cockroaches do. They won’t even try to approach food left outs because they can’t chew them nor process them into an available source of energy.
Any solid food is immediately ruled out, including wood, human hair, and dead insects. But what about eating each other or sucking up blood from each other? This is something bed bugs do not do, either. They take meals directly from humans and other mammals and do not eat each other. Since insects have hemolymph instead of blood, they can’t live on anything other than human blood and its equivalent in other warmblood species.
Scientists call them obligate hematophagous ectoparasitic insects. In other words, they are obligatory blood-feeders because blood is the only source of protein, energy, and water. They have effective and very active enzymes that digest blood, and a specialized digestive system evolved to do the job.
What happens in a bed bugs’ digestive system?
A bed bug’s digestive system is specialized to get from the blood all of the nutrients they need to keep on living. However, it shares a similar structure than other insects. It is composed of three regions called foregut, hindgut, and midgut. Out of the three, the midgut is the equivalent of the intestines, where the digestive function happens. This area can synthesize enzymes that break down blood particles and absorb their nutrients.
The midgut is then divided into three parts, anterior, middle, and posterior. The middle midgut plays a mechanical role while the anterior and posterior midgut secretes enzymes and absorb the nutrients. Carbs are absorbed in the anterior midgut while fat and proteins are absorbed in the posterior midgut.
An interesting fact about bed bugs’ digestive system is that the midgut has a defense mechanism against blood. When stored in the bed bug’s intestines, the blood releases toxic particles, primarily free radicals. But the digestive system of the bed bug is specialized to neutralize them with a complex system of vesicles called hemoxisomes. This allows bed bugs to feed up on human blood without any toxicity or harmful effects.
According to studies, they need to feed on blood every 5 minutes for each meal. That’s why they leave more than one bite every time they feed. When they are full, the middle part of the body is filled with blood, which is digested for the following 5 to 6 days. In the process, they start to feel the instinct to search for a new meal at an interval of 3-7 days.
Bed bugs feed on blood from mammals and birds, and nothing else. They cannot chew so that they won’t feed off solid particles, and they do not eat each other. Their digestive system is specialized to absorb nutrients from blood, and it also has an interesting mechanism that neutralizes toxic particles in the blood. Their digestion is completed after 5-6 days, and in this interval, they start feeling the instinct to search for a new meal.
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Santos, H. P., Rost-Roszkowska, M., Vilimova, J., & Serrão, J. E. (2017). Ultrastructure of the midgut in Heteroptera (Hemiptera) with different feeding habits. Protoplasma, 254(4), 1743-1753.
Reinhardt, K., & Siva-Jothy, M. T. (2007). Biology of the bed bugs (Cimicidae). Annu. Rev. Entomol., 52, 351-374.