When it comes to mosquitoes, most of us think only of the small blood-sucking pests that plague us in the evenings. This isn’t true for all mosquitoes, though.
The Culicidae mosquito family consists of approximately 3500 different species that form part of the fly order: Diptera. Like the rest of the fly order, mosquitoes are two-winged insects with small, soft bodies. Unlike most other flies, however, mosquitoes have several distinguishing features that help them stand out.
General Characteristics of the Culicidae Family
Most members of the mosquito family are known for their impact on public health. Because of the blood-sucking habits of female mosquitoes, these insects can transmit serious diseases, such as yellow fever, Zika, malaria, filariasis, dengue, and more.
The bodies of adult mosquitoes are slender and elongated. They’re almost fully covered with scales, including their veiny wings. They have long, fragile legs and piercing mouths.
In most Culicidae species, the male mosquitoes are smaller than the females and have noticeably bushier antennae. The males also typically feed on plant nectar and other juices, so they’re harmless to people and other animals.
In most mosquito species, though, female mosquitoes need animal blood. This is a source of protein that’s necessary to develop their eggs. Depending on the species, female mosquitoes might have preferences about the source of this blood. Some species prefer birds or reptiles while others have no preference and feed on all types of mammals, birds, and reptiles.
These differences between the various Culicidae species can be quite drastic, which is why it’s hard to speak about the family as a whole. There are three important mosquito genera within this family: Anopheles, Aedes, and Culex. Below, we’ll take a detailed look at the Culex mosquitoes, which is a major and widespread genus.
According to the Mosquito Taxonomic Inventory, the Culex genus includes 769 species of mosquitoes divided into 26 different subgenera. Of those 769 species, none are known carriers of malaria (which the Anopheles genus commonly carries) or of yellow fever (the Aedes genus is responsible for transmitting this disease). However, the Culex genus is still a carrier of viral encephalitis and filariasis. This makes the Culex genus a less-threatening but still medically important genus of the Culicidae family.
Culex mosquitoes are among the most widespread species of mosquitoes, found virtually everywhere on the planet. They aren’t found in the most northern and extremely cold regions (unlike Aedes and Ochlerotatus mosquitoes).
As a very versatile and adaptive species, most members of the Culex genus can lay eggs and live in both permanent and semi-permanent bodies of water. A large number of species can also live on leaf axils, in tree, rock, or crab holes, and even in flower pots. Their adaptability is what makes the Culex genus so widespread. Several species of this genus (like the filarial vector Culex quinquefasciatus) have even adapted to organically polluted waters.
The bodies of Culex mosquitoes are easy to distinguish thanks to several features, the chief among which is their posture. Culex mosquitoes hold their bodies parallel to the surface that they’re standing on, unlike Anopheles mosquitoes, which stand at a 45º angle to the surface. The bodies of Culex mosquitoes are uniform in color and lack many of the colorful stripes and spots of other genera. The tip of the Culex female’s abdomen is blunt and has retracted cerci (sensory appendages).
The lifecycle of a Culex mosquito typically lasts between 10–14 days, but can be longer in colder climates.
Culex Larvae and Eggs
Like with other members of the Culicidae family, Culex mosquitoes lay their eggs on the surface of a body of water. These eggs are usually gathered in masses of a hundred or more. The aquatic larvae or wrigglers will hatch from the eggs, swimming with jerking and wriggling motions. Unlike other flies and insects, mosquito larvae are active swimmers. In most species of the Culex genus, the larvae feed on algae and organic debris in the water, but some are predatory and can even feed on other mosquitoes. While in the water, they breathe through tubes on their thoraxes.
The duration of the pupal stage will vary, depending on the particular species. Most mosquitoes are ready to mate almost as soon as they emerge from their pupal cases.
As with other genera of mosquitoes, female Culex mosquitoes are the ones that suck blood from humans and other animals. The host’s body moisture, lactic acid, carbon dioxide, body heat, and movement seem to attract them. Some Culex mosquitoes feed only on birds or reptiles, but most don’t limit their protein sources and will feed on humans as well. Female Culex mosquitoes rarely hesitate to enter houses. They’re also smart enough to feed during after dusk when it’s dark and harder to see them.
The wider the feeding habits of a mosquito species, the more dangerous they typically are. Mosquitoes that limit themselves to a single or a few food sources have less medical importance as they rarely take part in the interspecies spreading of diseases.
The Culex genus and Disease Relations
Even though Culex mosquitoes don’t spread dreaded malaria or yellow fever, several species are still dangerous. This is particularly true for members of the Melanoconion subgenus. This is the largest Culex subgenus, including 160 species, which are widespread in Neotropical regions and parts of the southern USA. These are important vectors of encephalitis and other arboviruses.
Known vectors of the Japanese encephalitis virus include Culex fuscocephala, Culex gelidus, Culex tritaeniorhynchus, Culex pseudovishnui, and Culex vishnui. Known vectors of the West Nile virus in North America include Culex pipiens pipiens, Culex pipiens quinquefasciatus, and Culex tarsalis.
With several other species of Culex mosquitoes also involved in the spreading of diseases and arboviruses, the Culex genus is definitely not harmless, even if they aren’t as dangerous as Anopheles or Aedes mosquitoes.