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Insectsecological relationship

Invasive mosquitoes and range shift

Found, breeding, established, transmitting. Four different states, and most introductions stop early.

Mosquitoes carried to new places by trade and travel. The thing worth understanding is that being found, breeding, becoming established and transmitting disease are four separate states — and most introductions stop well before the last.

Mosquitoes arrive in new countries constantly. They travel in shipped goods, in used tyres holding a little water, in ornamental plants, in vehicles and in aircraft, and surveillance across Europe has recorded introductions repeatedly for decades. Most of them come to nothing: the individuals die, or they breed for a season and the population does not survive the winter. Some persist temporarily. Some establish permanently and then spread. Which happens depends on the climate they land in, on how much introduction pressure continues, and on how quickly anybody notices. That variety of outcomes is why the states must be kept apart, and it is the most useful thing this page offers. **Detected** means individuals were found. **Breeding detected** means they reproduced locally — larvae, or an emerging generation. **Established** means a population sustains itself across seasons, which in a temperate country means surviving a winter, usually as diapausing eggs rather than as adults. **Locally transmitting** means that population has passed a pathogen between people there, which also needs the pathogen present, enough infected hosts, and warmth enough for it to develop inside the insect. None of these steps implies the next. A detection is worth reporting, and is not the same news as an establishment. Two further distinctions save confusion. The species people merge are not interchangeable: the Asian tiger mosquito tolerates cool temperate conditions and has established across much of Europe, while Aedes aegypti is far more restricted by cold. And climate suitability describes conditions rather than occupancy — a place can be suitable and empty, and a place can hold mosquitoes all summer without being somewhere they survive a winter.

Early coverage · 66% complete · reviewed 2026-09-04

What this page covers

Chiefly Aedes species moved by trade and travel. The two most often confused — Aedes aegypti and the Asian tiger mosquito, Aedes albopictus — differ substantially in cold tolerance and in how far they have spread.

Often confused with: One category of "tropical mosquito", when the species differ in what they can survive; Detection meaning establishment, which is the central error this page exists for; Establishment meaning disease transmission, which is a further separate step

Quick facts

Four separate states
Detected · breeding · established · locally transmitting
Not a one-way ladder
Populations have been detected, controlled and eliminated
Two different species
The tiger mosquito tolerates cool climates; Aedes aegypti much less so
Suitable is not occupied
A climate model describes conditions, not presence

Four states, and what each actually requires

The distinction that decides what a detection means.

Finding a mosquito is not a breeding population. Breeding is not establishment. Establishment is not local disease transmission. Each step is a separate question needing its own evidence.

Established

Specialists would state this without hedging. Multiple independent lines of evidence agree.

Invasive mosquito surveillance distinguishes detection of individuals, confirmed local breeding, establishment of a self-sustaining population persisting across seasons including overwintering, and local transmission of a pathogen by that population. Progression between states is neither automatic nor inevitable, and each requires its own evidence.

Who this applies to
Invasive mosquito surveillance; the same state distinction applies to introduced species generally.
Studied in
Culicidae, Aedes aegypti, Aedes albopictus
Why we rate it this way, and what the caveats are
EstablishedHigh confidence

A standard surveillance framework, and the European record contains introductions that halted at each stage.

How far it can be extended

European surveillance records document introductions that stopped at each of these stages.

Caveats

  • The states are not a one-way ladder: populations have been detected, controlled and eliminated, and detection can recur without progression.
  • Absence of a later state is not evidence it cannot occur; it is a statement about what has been observed so far.

Still unanswered

  • What best predicts whether a given introduction will establish, which remains only partly answerable in advance.

Last reviewed 2026-09-04

The evidence (2 studies)
What each state means, and what evidence establishes it
StateWhat it meansWhat would show it
DetectedIndividuals found in a placeAdults or larvae identified by surveillance
Breeding detectedThey reproduced locallyLarvae, or an emerging local generation
EstablishedA population sustains itself across seasonsPersistence through winter, usually as diapausing eggs
Locally transmittingThat population passed a pathogen between people locallyCases with no travel history, linked to local vectors

Diagram

Four states — and moving between them is not automatic

Which have been reached, and what each would require.

Four states — and moving between them is not automaticDetectedIndividuals foundReachedBreeding detectedThey reproduced locallyReachedEstablishedPersists across seasonsNot reachedLocally transmittingPathogen passed between peopleNot reachedSolid rows are reached; dashed are not. Each needs its ownevidence, and progression can stop or reverse.
The same explanation in words

Four states are listed vertically with dashed arrows between them, marked as not automatic. Detected — individuals found — is shown as reached. Breeding detected — they reproduced locally — is shown as reached. Established, meaning a population persisting across seasons, is drawn with a dashed outline and marked not reached. Locally transmitting, meaning a pathogen passed between people, is also dashed and marked not reached. A note records that solid rows are reached and dashed ones are not, that each state needs its own evidence, and that progression can stop or reverse.

The last row needs the most conditions of all, and they are frequently skipped in reporting. Local transmission requires an established population, the pathogen present in enough infected people for a mosquito to acquire it, and temperatures high enough for long enough for the pathogen to develop inside the insect before it dies. A vector-capable species being present is one of four requirements, not the whole of it.

Two species, routinely merged

And the difference is exactly the one that matters in a cold country.

Aedes aegypti and the Asian tiger mosquito are different species with different limits. The tiger mosquito tolerates cool temperate conditions and has established widely in Europe; aegypti is far more restricted by cold.

Established

Specialists would state this without hedging. Multiple independent lines of evidence agree.

Aedes aegypti and Aedes albopictus differ in distribution and in thermal tolerance. Aedes albopictus persists in temperate regions, overwintering as diapausing eggs in cooler climates, and has established across much of southern and central Europe. Aedes aegypti has a substantially more restricted, largely tropical and subtropical distribution.

Who this applies to
Global distributions and thermal limits of the two species.
Studied in
Aedes aegypti, Aedes albopictus
Why we rate it this way, and what the caveats are
EstablishedHigh confidence

Distributions are well documented and the difference in cold tolerance is consistent across sources.

How far it can be extended

Established by compiled global occurrence records and by survival modelling for both species.

Caveats

  • Both distributions have continued to change since the sources were published.
  • Overwintering strategy differs as well as adult tolerance, and it is often the deciding factor for establishment.

Still unanswered

  • How far Aedes aegypti’s effective cold limit can shift through local adaptation, which is not well constrained.

Last reviewed 2026-09-04

The evidence (2 studies)

The Asian tiger mosquito, Aedes albopictus, overwinters as diapausing eggs in cool climates and has established across much of southern and central Europe. Aedes aegypti is substantially more restricted by cold and has a largely tropical and subtropical distribution. A question about one is not a question about the other, and headlines about "tropical mosquitoes" generally do not say which they mean.

Related

Suitability, arrival, and why both are needed

A climate model cannot tell you what is there.

A place can be climatically suitable for a species and hold none of it, because nothing arrived or arrivals did not persist. Suitability describes conditions; occupancy is a separate question.

Established

Specialists would state this without hedging. Multiple independent lines of evidence agree.

Climate suitability models estimate whether environmental conditions permit population persistence. They do not incorporate introduction pressure, dispersal, local control or biotic interactions, so suitability is neither necessary nor sufficient evidence of presence, and modelled suitability should not be reported as distribution.

Who this applies to
Species distribution and climate suitability modelling generally.
Studied in
Culicidae, Animalia, Plantae
Why we rate it this way, and what the caveats are
EstablishedHigh confidence

A well-understood limitation of the method, stated by its own practitioners.

How far it can be extended

A methodological property of suitability modelling rather than a fact about any taxon.

Caveats

  • The converse also holds: a species can persist in a place a coarse model marks unsuitable, often through urban microclimates.
  • Suitability estimates are sensitive to model structure and to the climate data used.

Still unanswered

  • How much urban microclimate extends effective suitability beyond what regional climate data imply.

Last reviewed 2026-09-04

The evidence (2 studies)

Establishment needs two independent things: somewhere the species can persist, and the species actually arriving there — repeatedly enough for one attempt to succeed. Suitability models address the first and are silent on the second, which is why a map of suitability is not a forecast of presence. Introduction pressure is the other half, and it comes from trade routes and travel rather than from climate.

The reverse case is worth stating too. Urban environments are warmer than the surrounding countryside, and small artificial water containers persist through conditions that would dry a natural pool. A species can therefore hold on in a city that regional climate data would mark unsuitable, which is one reason surveillance concentrates on ports, transport hubs and built-up areas rather than following a map of climate alone.

How unusual mosquitoes get noticed

Surveillance, and the public.

Official surveillance concentrates where introductions are likeliest — ports, airports, motorway service areas, tyre importers — using traps and larval surveys. It is deliberately targeted rather than comprehensive, because comprehensive is not affordable, which means the records show where people looked as well as what is there.

Public reporting supplements it. In Britain, unusual mosquitoes can be reported to the Mosquito Watch scheme run by the UK Health Security Agency, and records from the public contribute to the national picture of mosquito distribution. This site does not reproduce identification guidance: telling species apart reliably needs a specimen and a specialist, and the useful public contribution is the report rather than the identification.

Claims about this, checked

Things people have heard, and what the evidence actually supports.

The research behind this page

5 studies, newest first. Each one has a page explaining what it found and what it could not show.

2026UK Health Security Agency

Aedes aegypti breeding detected in England: surveillance statement

Aedes aegypti was confirmed breeding in Britain for the first time, at residential properties in east London.

2019Journal of the Royal Society Interface

The UK’s suitability for Aedes albopictus in current and future climates

Modelled suitability for Aedes albopictus in the UK is currently limited and concentrated in the warmest parts of southern England, and increases under warmer future scenarios, with the length of the suitable season a key constraint.

2015eLife

The global distribution of the arbovirus vectors Aedes aegypti and Ae. albopictus

The two species have distinct global distributions and distinct predicted suitability.

2013Parasites & Vectors

Modelling adult Aedes aegypti and Aedes albopictus survival at different temperatures in laboratory and field settings

Adult survival for both species declines sharply outside a limited temperature range, with the temperature response differing between the species and field survival generally lower than laboratory survival at equivalent temperatures.

2012Vector-Borne and Zoonotic Diseases

A review of the invasive mosquitoes in Europe: ecology, public health risks, and control options

Introductions have occurred repeatedly via international trade — notably the used tyre and ornamental plant trades — and shipping and road transport.

This page is a stop on a longer route

A guided journey reads several subjects in a deliberate order, with an argument for why one follows another. You can join in the middle.

Where to go from here

Each of these follows from something on this page — a relationship in the evidence, a claim people ask about, or the next mechanism along.

How complete this page is, and what it is still missing

NatureHQ publishes its own gaps. This page is at 66% completeness against what we would call a finished subject, and was last reviewed on 2026-09-04. It carries 4 claims and answers 10 mapped search questions.

  • more experiments could be explained in plain English
  • Other invasive mosquito species in Europe, including Aedes japonicus and Aedes koreicus, are not covered.
  • The Asian tiger mosquito has no page of its own yet, despite being the more widely established of the two.
  • Control methods are deliberately out of scope; this site explains biology rather than operational response.