On the 30th of March, we had the chance to meet Mr. Jean Michel Bérenger, a bed bugs specialist. This passionate and recognized entomologist has given us his time to answer a lot of our questions in his laboratory at the IHU (Institut Hospitalo-Universitaire Méditerranée Infection).
What are the main bed bugs species, and what differences can we spot?
The two main species of bed bugs are Cimex hemipterus and Cimex lectularius. These two species are the most studied and most likely to be the cause of infestation. There are no morphological differences (at least not with the naked eye), nor any metabolic differences between them. Thus, a basic bug trap can attract both.
It is already known that Cimex hemipterus is originally found in Russia and Sweden. The same goes for Cimex lectularius. It is assumed that the first individuals of these species appeared in these countries.
What do bed bugs feed on?
Like mosquitoes, bed bugs are exclusively hematophagous insects. Even though humans are the first victims, they can survive by feeding on the blood of other animals, such as cats, dogs, birds and even the gecko. It has been shown that with bed bugs feeding on non-human blood, the number of females’ spawning decreased and that the different stages of their development cycle were longer.
What are the essential nutrients for their survival and how are they assimilated?
Bed bugs draw vitamins A and B from their blood meals, essential for their survival. The blood digestion will be done thanks to symbionts that they carry in them at the intestine in the mycetoma. These symbionts will draw essential nutrients from the blood.
The insect’s body is at room temperature (22/24°C). A hematophagous insect should instantly die by thermal shock with a 37°C meal (Humans’ blood). An adaptive temperature regulation system is set up: specific to each hematophagous insect. For bed bugs, this mechanism is maintained by a ‘’Heat Shock Protein’’ (HSP) that sucks in the occurring thermal shock, protecting its environment.
We know that bed bugs have a carapace, what is it made of?
The bed bug shell consists of chitin and hydrocarbons at all stages of its development cycle. Moreover, one of the major phenomena of resistance in bed bugs is the thickening of the cuticle. The treatment used to eradicate them will have more difficulty to penetrate, and therefore will be less efficient.
What about the phenomenon of resistance?
The bed bugs’ resistance phenomenon is mainly caused by humans. If you use a lambda insecticide on a wild bug, it dies instantly, which is not the case with some bed bugs. This is because most people use products with molecules to which the bug resists, which maintains its resistance somehow. So, from the outset it must be known with which individual we are dealing. Thanks to their strong sense of smell, some dogs can spot bed bugs’ larvae and adults, even through a double wall.
What are bed bugs attracted to?
Bed bugs are guided to us by 3 main factors: CO2, temperature and odors. In addition, recent studies have revealed their attraction to colors, such as red and black as well as contrasts (juxtaposed black and white). This attraction would be explained by a camouflage behavior.
Finally, the pheromones are very important. The black spots that can often be found around the areas where they are, are made of their own droppings. It is digested blood, containing pheromones that are very detectable particles by bed bugs. This detection can be done in a very wide area around the point of emission. After a series of meal hunting, they use the pheromones released by their droppings to guide themselves back and find their dark den. They capture the pheromones via their antennas.
What are the optimal conditions for bed bugs’ development cycle?
Bed bugs live at room temperature (about 25°C). Some people think that lighting is a very important parameter, while others feel that it is not, since originally these insects live in dark caves with bats.
When are bed bugs the most vulnerable in their life cycle?
Bed bugs are the most vulnerable in their first stages of life. It is at this point that individuals exhibit a high metabolic activity that decreases as one goes through the life cycle. It is therefore easier to target metabolic pathways essential to the individual during these life stages.
Which microorganisms are bed bugs sensitive to?
They are not sensitive to viruses, but a recent study has been conducted on their contamination by bacteria and especially by pathogenic fungi, for example Beauveria bassiana.
Do they Interact with other insects? Do they have any predators?
Bed bugs live inside our houses; thus, they don’t interact much with other insects. The House Centipede (Scutigera coleoptrata) is one of its natural predators, but I do not think anyone agrees with the idea of bringing them inside their home to get rid of bed bugs.
What about their evolution cycle?
Bed bugs are insects that have become simpler over time. They have no more wings, no more complex eyes but compound eyes, compared to their wild counterparts. Set over against triatoma (wild hematophagous bugs in the Amazon jungle), they only have about fifty pheromone sensors. Their wild counterpart has more than 3000. This is a good example of simplification; bed bugs are no longer in need for wings and many sensors since their prey, us humans, is a few steps away.
Are bed bugs pathology vectors?
To date, no pathogen can be transmitted by the bite of a bed bug, since there is none in the salivary glands. Pathogens are only found in their droppings and intestines.
What are the limits of the solutions?
The use of gas is misguided, because bed bugs can also hide behind a piece of furniture against the wall, where the gas does not reach. Individuals will not all be affected.
There is already a passive trap that puts together an odorant tube (coriander odor) and an adhesive tape. It’s an interesting solution for the bugs that have just arrived in the room and have not yet installed. Otherwise, the use of an active trap (CO2, temperature, odor) is more efficient. These traps already exist (heat and smell) but are more or less effective. On the other hand, there is not yet a trap putting together the three attraction factors of bed bugs.