How Do Mosquitoes Bite?

Mosquitoes are small flying insects that are known for their blood-sucking habits. They are responsible for transmitting diseases to over 700 million people annually, leading to the deaths of over one million people worldwide. When a mosquito bites, it injects a small amount of saliva into the skin, which can cause an itchy, red bump to appear. But have you ever wondered how exactly do mosquitoes bite us? How do they locate their hosts and what happens during the biting process?

HOW DO MOSQUITOES FIND US?

Mosquitoes are experts at finding their victims. They use their antennae, maxillary palps, and proboscis to find a host. These structures carry olfactory receptor neurons (ORNs) that contain olfactory receptor proteins (ORPs). The ORPs are capable of detecting odor molecules and leading the mosquito to a host.

Mosquitoes use both chemical and visual cues to find their host.

The chemical cues are:

⦁ the carbon dioxide we breathe out,

⦁ the lactic acid in our sweat,

(Lactic acid is considered a mosquito attractant according to this study and a mosquito repellent according to this study.)

⦁ 1-Octane-3-ol in our breath and sweat,

⦁ heat and volatile compounds given off by our bodies,

⦁ moisture,

⦁ and bacteria on our skin.

HOW DO MOSQUITOES BITE US?

Mx - Maxilla; M - Mandible; H - Hypopharynx.

Image Credit: Frontiers | Multitasking roles of mosquito labrum in oviposition and blood feeding (frontiersin.org)

Almost everyone knows that mosquitoes have a long appendage at the front that they use to suck their host's blood. This appendage is called the proboscis. The proboscis is often thought of as one simple organ, but it is actually a complex organ composed of six different parts, each of which is known as a stylet and collectively as fascicle.

The structures outside the proboscis are:

LABIUM: Labium is the outer sheath of the proboscis. It folds back when the skin is pierced by the fascicle.
LABELLA: Labella are two sensory probes at the tip of the probosci

The structures that make up the proboscis are:

MAXILLAE: Maxillae are paired structures. These are serrated or saw-like and are used to saw through the skin.
MANDIBLES: Mandibles are also paired structures. These structures hold the tissue apart while the maxillae saw through the skin.
LABRUM: The labrum has receptors that can detect blood and it leads the mosquito directly to the nearest blood vessel. Once, a blood vessel is detected, the mosquito uses its labrum to pierce it and suck the blood.
HYPOPHARYNX: The role of the hypopharynx is to transfer saliva to the tissue of the host through the salivary canal present on its dorsal surface. The transfer of saliva is important because it prevents blood coagulation.