There are two species of bed bugs that have been resurging worldwide in the past two decades: tropical bed bugs (Cimex hemipterus) and common bed bugs (Cimex lectularius). Both species feed predominantly on humans and have similar behaviors; they both hide and aggregate in cracks and crevices; they both suck blood; and they both have the same life cycle — starting as eggs, developing into five different instars and finally molting to an adult.
Both of these species also are important from a public health perspective because their bites can cause itchy, rash-like reactions and many people who experience bed bugs often suffer from psychological distress. This distress has been reported as ranging from loss of sleep, anxiety, to even depression. Although tropical bed bugs and common bed bugs are similar, these species do have some marked differences.
First, both species seem to dominate in different areas of the world. The tropical bed bug, as the name suggests, lives in more tropical regions. This species dominates in areas of Asia, Africa and South America. The common bed bug dominates in more temperate climates and is the species we are the most familiar with in the United States. Thus far, the common bed bug has spread to all 50 states. A recent survey conducted by the National Pest Management Association with the University of Kentucky showed that two out of three pest management professionals in the United States believe that bed bug infestations are still increasing in number.
Bed bugs, regardless of the species, are moved around by people. The resurgence of bed bugs has been attributed to travel, increased insecticide resistance and changes in pesticide practices. Undoubtedly, the introduction of one species is similar to the other; they are both moved around the world in people’s luggage, backpacks, purses and other belongings. Therefore, tropical bed bugs certainly have been brought into the United States periodically, but have yet to either skyrocket in number like the common bed bug or they may have just been overlooked.
HOW THEY’RE DIFFERENT. A tropical bed bug infestation would look just like a common bed bug infestation. You would see live bugs potentially, depending on the level of infestation, and these live bugs would look just like a common bed bug to the untrained eye/without a microscope. You may even see the dark black fecal spots as well as the exuvia, or shed skins — remember both species are similar. However, once you get the bed bugs under a microscope — or maybe even a good hand lens — then you would see the tell-tale difference. The tropical bed bug’s “neck” or pronotum, just behind the head, is a different shape than the common bed bug. The common bed bug has a more excavated, or u-shaped pronotum.
The tropical bed bug has often been said to be in the United States, but no recent publications or documents have reported this since the 1940s until recently. After a 70-year absence, we (University of Florida researchers) received a sample of bed bugs that didn’t look quite like we were accustomed to seeing. After careful examination, we realized we had tropical bed bugs and then contacted the homeowners. According to the homeowners, no one in the house had traveled out of the United States or Florida. Thus, it seems like the tropical bed bug had established elsewhere in Florida and the homeowners had unknowingly brought them into their home.
Identification can be accomplished when the bed bugs are magnified. However, the differences are not pronounced, so it would be best to send samples to an extension office associated with a university. Many of the identification keys are not very straightforward and require the pronotum to be measured to ensure positive identification, especially in specimens where the pronotum shape cannot be easily differentiated between the two species.
FINAL THOUGHTS. There is still little known about tropical bed bugs. Much less research has been performed with this species compared to the common bed bug. It has been suggested that tropical bed bugs lay fewer eggs but develop faster than common bed bugs, potentially explaining their distribution differences world-wide. However, bed bug development times can vary when temperatures fluctuate or fluctuate even when bed bugs have been exposed to different insecticides. For instance, bed bugs with high levels of pyrethroid resistance have been shown to lay fewer eggs than their less-resistant relatives.
For now, until more research has been conducted, the same control measures that are are used against common bed bugs should potentially work against tropical bed bugs. Their similar biology should still allow many of the tools that we have found to work previously to be effective, including heat treatments, fumigation and chemicals. Of course, resistance is still an issue with tropical bed bugs, so rotating products may be necessary to gain control.
While tropical bed bugs have been documented in Florida, they have the potential to spread to other areas of the United States. Subtropical areas in other southern states could harbor this species, and homes with temperature-controlled climates inside also could help this species spread beyond its normal tropical distribution. Proper identification and awareness will help researchers and the industry alike determine whether this species will continue to spread and to determine if it is currently prevalent in other areas and potentially has been overlooked.
The author, Brittany Campbell, is a UF/IFAS doctoral student in entomology.