The systematics of Culex quinquefasciatus, a member of the Culex pipiens complex, are a little confusing. That species was known as Culex fatigans and that name is often still used in the European literature. Cx. quinquefasciatus has spread across the tropics associated with people and hybridized with local related species (eg. Culex pipiens pallens) or other invasives (Culex pipiens). Some authors also refer to it as Cx. pipiens quinquefasciatus.
Professor Dave Chadee (PhD, London), medical entomologist of the University of the West Indies in Trinidad is a Culex expert and will be familiar with species distribution in the Caribbean and South America.
Culex quinquefasciatus was Nomina Dubia, till somebody advocated that it is a Culex per say. Read the original account and it is clear that it is not a Culex . The original type specimen is missing in the depository. Any way it is not a species but a subspeies of Culex pipiens anterbreed freely from all geographical areas of C. pipien distribution
Dear Dr. Aslamkham, I am afraid I must disagree with you. The presence of hybrids does not per se negate the existence of separate species, as even Ernest Mayr asserted in his later writings. The two species Culex pipiens in the north and Cx. quinquefasciatus in the south maintain clearly separate populations linked by more or less extensive hybrid zones (that was the requirement that Mayr attached to his definition of species when hybridization was apparent). In addition although it is true that Culex quinquefasciatus Say's type specimen is indeed missing a neotype has been designated and is in existence at the NMNH, Smithsonian Institution in Washington, DC from specimens collected in New Orleans, USA. Please refer to ms by Sirivanakarn&White1978 at this url: http://ww.w.sandflycatalog.org/files/pdfs/122850-0.pdf which includes the original description by Say, which although not as complete as one might hope (but maybe ok for 1823) does fit Cx. quinquefasciatus.
However, I have identified two broadly genetically distinguishable populations of Cx. quinquefasciatus across the World divided between the New World and the Old World and evidence of different degrees of mixing between them (please refer to Fonseca et al 2006 in my ResearchGate page). Their morphology is, from what I can tell, the same but different genetic makeups appear to differ in vector competence (for example to bird malaria) and vectorial capacity (for example, likelihood to bite birds vs. mammals).
You can find the systematic of mosquito species on sodh ganga. There is a thesis on mosquito systematic submitted by Dr. gavendra Singh from Dayalbagh Educational Institute, Agra.