Lesson 8 of 9 / Climate change, food and disease vectors
Connect temperature to the mosquito life cycle
Why does warmer not always mean more mosquitoes?
In this lesson: Explain insect metabolism, temperature tolerance and temperature-dependent Aedes aegypti development.
About 6 min
The key ideaWithin suitable limits, warming can increase insect metabolic and developmental rates. Beyond tolerance limits, survival falls; Aedes development also requires the right life-stage habitat.
Explore the idea
Follow development and survival
Eggs are laid on surfaces near the waterline. Flooding can trigger hatching.
14 daysDevelopment time among survivors
90 / 100Reach adulthood from the starting cohort
Development is slower, but 90 of 100 survive in this invented cohort.
All values are original teaching data, not measured Aedes temperature thresholds. Faster development and higher survival are different outcomes.
Explanation
Insects are ectotherms: environmental temperature strongly influences their body temperature. Within a suitable range, warmer conditions can increase enzyme activity and metabolic rate, often speeding feeding, growth and development. Their processes still have lower and upper limits, so the response cannot be extrapolated indefinitely.
Aedes aegypti develops through egg, larva, pupa and adult stages. Females lay eggs on surfaces near the waterline in suitable containers. Flooding of the eggs can trigger hatching; larvae and pupae live in water, while adults emerge and fly. The female takes blood meals that support egg production.
Moderate warming can shorten development time and allow more generations during a suitable season. It can also change adult feeding frequency and survival. At excessive temperatures, damage, dehydration or reduced survival can offset faster development; breeding water may also dry up.
Temperature tolerance differs among insect species and life stages, but each has a limited range for successful development. A useful interpretation considers both speed and survival. The fastest development among survivors need not produce the most surviving adults from the original eggs.
The diagram uses invented teaching data to separate these effects. They are not measured Aedes thresholds or a prediction for a particular town. Rainfall, container water, food, crowding and control measures would also affect real populations.
Step by step
- 1
Locate the life stage
Eggs near water, aquatic larvae and pupae, then a flying adult.
- 2
Consider rate within the range
Warming can speed metabolism and development.
- 3
Check survival and habitat
High-temperature stress or dry breeding sites can reduce successful emergence.
Worked example
Fast development is not the only outcome
In an original model, a cohort develops in 9 days with 85% survival at condition B, and 7 days with 60% survival at warmer condition C. Which produces more adults from 100 starting individuals?
One way to explain it
B produces 85 adults and C produces 60. C has faster development among survivors but lower survival, so development time alone is insufficient to predict adult production.
Why this answer works
- Use the same starting cohort size.
- Compare emergence count as well as development time.
- Do not turn illustrative conditions into real species thresholds.
Is this true? "Raising temperature always increases the mosquito population without limit."
Benefits occur only within suitable conditions. Excessive heat, dehydration and loss of breeding water can reduce survival and reproduction.