Form molestus can live under ground and frequently bites mammals including humans, also known as the London Underground mosquito.

[8] In Californian molestus populations, it was shown that most females of C. pipiens do not enter reproductive diapause during the winter (homodynamy), which differs from other mosquito species, such as C. stigmatosoma or C. tarsalis.

[9] The practice of overwintering tends to vary based on location, and in effect temperature and the period of time per day an organism receives sunlight, also known as the photoperiod.

Because of this temperature condition, mosquito breeding seasons vary by region and climate characteristics of a given area.

The proboscis and wings are brown, matching the remainder of their body.Culex pipiens can be found in both urban and sub-urban temperate and tropical regions across the world.

[12] It is prevalent on most continents, including North and South America, Europe, and some areas of Asia and Northern Africa.

The Culex genus, and a large number of other mosquito species, thrive in mostly wet, humid, and temperate climates.

In California population, it was shown that most females of C. pipiens do not enter reproductive diapause during the winter, which differs from other mosquito species, such as C. stigmatosoma or C. tarsalis.

The practice of overwintering tends to vary based on location, temperature and the period of time per day an organism receives sunlight, also known as the photoperiod.

Stable pH values, salt content in water, and the temperature of the habitat's environment, are all factors that can either positively or negatively influence larval survival rates.

[13] Culex pipiens is a pollinator of Silene otites, tansy (Tanacetum vulgare), and Achillea millefolium.

These studies showed that C. pipiens are capable of surviving all of these metrics in extreme values, demonstrating their eurytopic nature.

The growth rates of larvae are dependent on factors including temperature, food and water provisions, larval density and characteristics of the breeding season they are born into.

Furthermore, measured rates of success of the complex has been associated with consumption of “food” found in standing water sources that have been developed by humans and livestock.

[24] At the end of the summer and the start of the fall season before it is time for them to overwinter, C. pipiens subsist on nectar and other sugary food sources in order to store fat.

Searching for sources of blood requires a complex of behavioral responses that influence C. pipiens sensory mechanisms that help them to locate hosts.

[citation needed] Garvin et al 2018 find C. pipiens to be more attracted to adult birds than nestlings, by differentiating between uropygial gland secretions of different ages (tested in Passer domesticus).

Because of this temperature condition, mosquito breeding seasons vary by region and climate characteristics of a given area.

In 1972, Lea and Evans[13] performed a study that yielded results showing that the number of inseminated females drastically increased with age.

Other breeding sites include: natural marshes, cesspits, gutters, and other unkempt artificial water structures.

According to Daniel Markowski from the Vector Disease Control International, “Culex pipiens larvae specifically thrive in such stagnant water with the most organic material pollution".

Increased larval densities also affected how many eggs were produced among females that survived within the original experimental population.

This trait varies across the C. pipiens complex, and could limit transmission of pathogens since females do not risk food contamination in order to lay eggs.

In the process of digesting blood, mosquitoes inject saliva instantly after the proboscis enters the host.

Cases of Rift Valley fever have been present in Africa, Japanese encephalitis has been prevalent in East Asian countries, and West Nile virus has been seen all over the globe.

[13] In February 2019, a theoretical modelling study was reported regarding the potential role of C. pipiens in transmitting West Nile Virus in the UK.