Bed Bug Bites
Bed bugs have piercing sucking mouthparts that are capable of causing a variety of different reaction in people. It’s generally thought that one in three people may not react at all to bed bug bites. To understand the range of reactions, it’s helpful to understand the process by which a bed bug acquires a meal.
The head of the bed bug is fitted with a tube-like structure known as the rostrum. It folds underneath the head of the bug when not in use (see diagram). When in use, it unfolds to a downward piercing position. Inside the rostrum there’s a pair of mandibles with serrated edges that cut into the host’s skin in an alternating motion. Once the skin is breached a pair of maxillae follow behind the mandibles, searching for a suitable blood vessel. The maxillae search for a blood vessel that’s neither too big nor too small. Once a suitable capillary is found, a salivary duct follows to inject an anti-coagulating saliva into the vessel to insure a constant flow of blood. A small pump (referred to as the cibarial pump) located in the head of the bug initiates a sudden jolt of suction, and blood immediately begins flowing up through a food canal. Blood continues to flow uninterrupted, thanks to the host’s own blood pressure.
This process of cutting, searching, and injecting anti-coagulating saliva is responsible for the variety of physiological responses in humans. Some people may be sensitive to the cutting and searching mechanical activity, while others may react to proteins in the saliva. Severe reactions are probably a response to all aspects of the encounter, while non-reacting hosts may not respond to any part of the process.