Culex is a genus of mosquito which like most other mosquitoes, serves as a vector for filariasis or encephalitis. It belongs to:
Physical Features
Culex sp mosquitoes have a distinct physical appearance, characterized by their small size, narrow, pointed wings with a white band, long, thin legs, and long proboscis. These features enable them to move quickly, navigate different surfaces, and feed efficiently on blood.
Culex mosquito can be differentiated from Anopheles and Aedes mosquito by observing the morphology- abdomen, wings, legs, length of proboscis, lengths of antennae and the metamorphic stages in each of the life cycle of these mosquito.
Size: Culex mosquitoes are relatively small, measuring around 3-4 mm in length. They have a slender and elongated body, which is covered in fine hair.
Proboscis: Culex mosquitoes have a long, slender proboscis that is used for feeding on blood. Palpi are 1/4 to half of the proboscis and slender in the shape (female) and longer than the proboscis (male).
Abdomen: Abdomen is blunt and with alternate white and black bands on it.
Wings: Wings of Culex mosquitoes is their narrow, have small black scales. Culex mosquitoes' wings are also relatively longer and narrower than other mosquito.
Legs: Culex mosquitoes also have long, thin legs that are covered in fine hair, which helps them to sense vibrations in their environment. Generally there are no white markings present on the legs.
Male and female Culex mosquitoes can be distinguished by observing their:
antenna- male- Culex has plumose antenna whereas female Culex has pilose antennae
proboscis- palps are shorter in case of female mosquito and longer in the male.
Habitat and Distribution
Culex mosquitoes can be found all over the world, with different species inhabiting different regions. They are widespread in North America, South America, Europe, Asia, and Africa. They are most common in areas with warm and humid climates, such as tropical and subtropical regions.
Culex mosquitoes are found in many parts of the world, including both tropical and temperate regions. They are known to breed in a variety of aquatic habitats, including stagnant or slow-moving water bodies such as ponds, ditches, marshes, and swamps. They can also breed in man-made containers such as discarded tires, buckets, and other water-holding objects.
Life Cycle
The life cycle of Culex mosquitoes is a complex and fascinating process that involves four distinct stages: egg, larva, pupa, and adult.
Egg Stage: Culex mosquitoes start their life cycle as eggs, which are laid by the female mosquito on the surface of stagnant water as a raft. Females typically lay their eggs in batches of 100-300, using a glue-like substance to attach them to the surface of the water. The eggs hatch within a few days, releasing the mosquito larvae.
Larva Stage: The larvae called WRIGGLERS are aquatic and develop in the water, feeding on small organic particles and microorganisms. They have a distinct appearance, with a slender, elongated body and a small head with mouthparts that they use to filter food particles from the water. They also have siphons that they use to breathe air from the surface of the water. The wriggler larva rests at an oblique angle just below the surface of the water.
The larvae go through four molts, shedding their chitin each time by process of
ecdysis and increasing in
size. The larval stage can last anywhere from a few days to several weeks,
depending on environmental conditions.
Pupa Stage: After the final molt, the larva transforms into a pupa, which is a non-feeding, aquatic stage that lasts for a few days. The pupa is the last stage of development before the mosquito emerges as an adult. During this stage, the pupa does not move and is enclosed in a protective case, known as the pupal case. The pupal case allows the mosquito to transform into an adult without being damaged by the water.
Adult Stage: Finally, the mosquito emerges from the pupal case as an adult. The adult mosquito has fully developed wings and is capable of flying. Females require a blood meal to develop their eggs, and they seek out hosts, including humans and animals, to feed on. Males, on the other hand, feed on nectar and plant juices. Adult mosquitoes live for several weeks to several months, depending on the species and environmental conditions.
Pathogens and Diseases
What makes Culex mosquitoes so concerning to humans is their potential to transmit diseases. Some species of Culex mosquitoes are known carriers of West Nile virus, which can cause severe illness in humans, particularly in older adults. They can also transmit other diseases such as St. Louis encephalitis and the filarial worm that causes lymphatic filariasis.
Few of Culex species are listed below along with their pathogen and diseases.
Vector Culex species | Pathogen(s) | Disease(s) |
Culex pipiens | West Nile Virus, St. Louis Encephalitis Virus, Eastern Equine Encephalitis Virus | Encephalitis (brain swelling) |
Culex quinquefasciatus | West Nile Virus, St. Louis Encephalitis Virus, lymphatic filariasis | Encephalitis, lymphatic filariasis (swelling of limbs and genitals) |
Culex tarsalis | West Nile Virus, Western Equine Encephalitis Virus | Encephalitis |
Culex nigripalpus | West Nile Virus, Eastern Equine Encephalitis Virus | Encephalitis |
Culex erraticus | Eastern Equine Encephalitis Virus | Severe encephalitis |
Culex salinarius | West Nile Virus, St. Louis Encephalitis Virus | Encephalitis |
Culex restuans | West Nile Virus, St. Louis Encephalitis Virus | Encephalitis |
Again, it's important to note that Culex mosquitoes are not the only vectors of these diseases, and other mosquito species may also transmit them in different regions.
Culex mosquitoes are widespread throughout the world, with their distribution influenced by factors such as climate, habitat availability, and human activities. They are commonly found in both natural and artificial water bodies, and their adaptability to different environments makes them a significant public health concern. Understanding their habitat and distribution is critical for controlling their populations and reducing the risk of disease transmission.