When speaking about mosquitoes, most of us think exclusively about the small blood-suckers that plague the evenings and nights of most people on Earth. This isn’t true for all mosquitoes, however.
The mosquito family – Culicidae – consists of approximately 3,500 different species that are a part of the fly order, Diptera. Similar to the rest of the fly order, mosquitoes are two-winged insects with small, soft bodies. Unlike most other flies, however, mosquitos 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 medical and public health importance. Because of the blood-sucking habits of female mosquitoes, these species are known to transmit serious diseases, such as yellow fever, Zika fever, malaria, filariasis, dengue, and others.
The bodies of adult mosquitoes are slender and elongated. They are almost fully covered with scales, including over the veiny wings. They have long and fragile legs, and piercing mouths.
In most Culicidae species, the male mosquito is considerably bigger than the female and has a noticeably bushier antenna on their heads. The males also typically feed on plant nectars and other plant juices and are harmless for people and other animals. In most mosquito species, however, female mosquitoes feed on animal blood in order to acquire protein that’s necessary for the development of their eggs. Depending on the species, females can also feed on plant nectar in addition to blood, or have a 100% blood diet. Also depending on the species, female mosquitoes can have preferences about the source of the blood. Some species restrict themselves to just birds or just reptiles, while others will show no preferences 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 – the Anopheles, the Aedes, and the Culex genus. Below, we’ll take a detailed look at the Culex genus, as one of the major and most widespread genera of mosquitoes.
Culex mosquito genus
According to the Mosquito Taxonomic Inventory, the Culex mosquito genus includes 769 species of mosquitoes, divided into 26 different subgenera. Of those 769 species, none are known to be carriers of malaria (which the Anopheles genus is a common carrier of) or of yellow fever (as the Aedes genus is). However, the Culex genus is still a carrier of viral encephalitis and – in subtropical climates – of 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 and can be found virtually everywhere on the planet, except in the most northern and extremely cold regions (where Aedes and Ochlerotatus can be found). 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 exclusively on leaf axils, in trees, rock- or crab-holes, and even in flower pots. This adaptability is what makes the Culex genus so well-spread. Several species of this genus (like the filarial vector Cx. Quinquefasciatus) have even adapted to organically polluted waters.
The bodies of the Culex mosquitoes are distinguishable by several features, chief among which is their posture. Culex mosquitoes hold their bodies parallel to the surface on which they stand, unlike Anopheles who stand at an angle with the surface. The Culex bodies are also 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 life cycle of a Culex mosquito is typically between 10 and 14 days but can be longer in colder climates.
Culex larvae and eggs
The eggs of Culex mosquitoes are laid similarly to other genera of the Culicidae family – on a water service and hatch into aquatic larvae or wrigglers. These swim in the water with jerking and wriggling motions. Unlike other flies and insects, mosquito larvae are active swimmers. Eggs are usually joined in masses of hundreds and more. 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 this pupal stage varies depending on the particular species, but most mosquitoes are ready to mate almost as soon as emerging from their pupal cases.
Like other genera of mosquitoes, female Culex mosquitoes are the ones that suck blood from humans and other animals. They seem to be attracted to the host’s body’s moisture, lactic acid, carbon dioxide, body heat and movement. Some Culex mosquitoes feed only on birds or reptiles, but most members of the genus don’t limit their protein sources and will feed on people as well. Female Culex mosquitoes rarely hesitate to enter houses and are smart enough to feed during after dusk when it’s dark and they are hard to notice.
The winder the feeding habits of a mosquito species, the more dangerous they typically are. Mosquitoes that limit themselves to a single or a few feeding sources have little medical importance as they rarely take part in the inter-species 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 and have medical importance. Particularly members of the Melanoconion subgenus (the largest Culex subgenus – it includes 160 species) that are widespread in Neotropical regions and parts of southern U.S. are important vectors of encephalitis and other arboviruses.
Culex fuscocephala, Cx. Gelidus, Cx. tritaeniorhynchus, and Cx. Vishnui are known to transmit Japanese encephalitis virus. Cx. tarsalis, Cx. Restuans, Cx. nigripalpus, and Cx. pipiens transmit encephalitis viruses in North America.
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 are not as dangerous as the Anopheles or Aedes genera.