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?
In this lesson: Explain insect metabolism, thermal tolerance and Aedes aegypti development.
About 7 min
The key ideaModerate 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?
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
Identify the life stage
Aquatic stages and flying adults face different conditions.
- 2
Locate the temperature range
Below, within or above a favourable range?
- 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.
Is this true? "Every increase in temperature increases mosquito numbers without limit."
Thermal tolerance, water availability and survival impose limits and can reverse the response.