9477 / 2027

Lesson 6 of 7 / Climate, biodiversity and disease ecology

Temperature and the Aedes life cycle

Why does warming help development only within a suitable range?

I can explain insect metabolism, thermal tolerance and Aedes aegypti development.

  • I can explain insect temperature responses and Aedes aegypti life cycles.Syllabus

    Syllabus 9477, Extension B(h). Explain insect temperature responses and Aedes aegypti life cycles.

About 7 min

Make a guess. You are not marked.

Warmer water speeds up Aedes mosquito development. Will hotter and hotter water keep increasing mosquito numbers?

  1. It will, until the water nears boiling.
  2. Faster development means more mosquitoes.
  3. Above their tolerance, survival falls.
Show the answer

Above their tolerance, survival falls.

Warmth speeds metabolism only within a suitable range. Beyond it, heat stress kills larvae and adults.

The key idea

Moderate warming can speed insect metabolism and development, but heat beyond tolerance reduces survival and does not increase risk indefinitely.

Trace the biological links

Which life stages need water?

Egg -> larva -> pupa -> adultEggs associated with breeding sites

Aedes eggs are associated with suitable water-holding sites; flooding can allow hatching. Conditions and egg survival influence the next generation.

Original schematic shapes. Larva and pupa develop in water; the adult is not an aquatic larval stage. Aedes transmits dengue virus, whereas malaria uses Anopheles vectors.

Explanation

Insect body temperature is strongly influenced by the environment. Within a suitable range, higher temperature generally increases enzyme-mediated metabolism, growth and development. Many insects, especially those adapted to relatively stable conditions, have limited thermal tolerances; different stages and species can respond differently.

Aedes aegypti develops through egg, larva, pupa and adult stages. Larvae and pupae develop in water, often in small containers; adults emerge and disperse. Adult females obtain blood meals needed for egg production and can transmit dengue virus when infected.

Warmer suitable conditions can shorten the time from immature stages to adult, potentially allowing more generations or faster population recovery. Temperature can also affect biting, survival and pathogen development within the mosquito. These influences can oppose one another, so faster development is not the same as guaranteed more transmission.

Above a favourable range, heat stress can damage proteins, increase water loss or reduce survival and reproduction. Water availability and rainfall patterns also determine breeding habitats. A temperature-response curve should therefore show a limited viable range rather than an endlessly rising line.

Step by step
  1. 1

    Identify the life stage

    Aquatic stages and flying adults face different conditions.

  2. 2

    Locate the temperature range

    Below, within or above a favourable range?

  3. 3

    Combine development and survival

    A shorter generation time helps only if enough survive and reproduce.

Worked example

Work through the evidence

Larval development time falls from 12 to 8 days with moderate warming, but at a higher temperature survival falls sharply. Interpret.

One way to explain it

Moderate warming speeds development within a suitable range, while excessive heat exceeds tolerance and reduces survival. Population outcome depends on both effects.

Why this answer works
  • Rate and survival are different variables.
  • Do not extrapolate the 12-to-8-day trend indefinitely.

Watch out for this

A student says: "Every increase in temperature increases mosquito numbers without limit." What is wrong with this?

Show the answer

Thermal tolerance, water availability and survival impose limits and can reverse the response.

Check your understanding

Which Aedes stages are aquatic in the normal life cycle?

  1. Larva and adult
  2. Egg and adult, but not pupa
  3. Larva and pupa
Show the answer

Larva and pupa

These immature stages develop in water before adult emergence.

Exam-style questions

Check your understanding

Invented data: Aedes larvae took 14 days to reach adulthood at 20 degrees C, 9 days at 26 degrees C and 7 days at 32 degrees C, but survival was 80%, 75% and 20%. Which conclusion is best supported?

  1. Temperature has no effect on mosquitoes.
  2. More adults are produced at 32 degrees C.
  3. Warmer water speeds development but can lower survival.
  4. Survival rises as development speeds up.
Show the answer

Warmer water speeds development but can lower survival.

Development time fell from 14 to 7 days, yet survival fell sharply to 20% at 32 degrees C.

Quick recall

Card 1 of 3. Answer in your head, then check.

Why does warming help development only within a suitable range?

You can return to this lesson any time.