From swimmer to flyer; this period is known as the mosquito’s quiet transformation. Once a mosquito larva completes its final moult, it enters the pupal stage, a remarkable phase of transition and reorganisation. Known informally as “tumblers”, pupae are unlike any other stage in the mosquito life cycle. They do not eat. They do not grow. But inside, everything is changing. For the Anopheles mosquito, this is a short but essential step in becoming a flying adult capable of seeking hosts; and, in the case of females, possibly transmitting malaria.

What is a mosquito pupa?

The mosquito pupa is a comma-shaped aquatic form. Its body is divided into two main parts: a rounded cephalothorax and a curled abdomen. The cephalothorax is the fused head and thorax region, forming a single, rounded structure that houses the new developing parts of an adult mosquito. It is the most prominent part of the pupa and is essential for the transformation process. Pupae are lighter than water and float just beneath the surface. At first glance, the pupa appears to do very little. But inside the cephalothorax, cells are rapidly dividing, and the body is being reorganised. Wings, legs, antennae, and reproductive structures are forming. This is metamorphosis in action.

Breathing, movement, and stage length

Like larvae, pupae are aquatic but air-breathing. Instead of spiracles, they breathe through two trumpet-like structures called respiratory trumpets located on the cephalothorax. These extend above the water surface to access air. Although pupae do not feed, they are far from passive. When disturbed, they tumble downward in a jerky, spiralling motion, hence their nickname “tumblers”. This sudden diving reflex helps them avoid predators and surface disturbances.

The pupal stage is relatively short, typically lasting 1 to 3 days, depending on environmental conditions like temperature. Warmer climates speed up development, while cooler water can delay emergence.

Inside the pupa, hormonal cues orchestrate the final stages of metamorphosis. Once transformation is complete, the adult mosquito is ready to emerge, but only under the right conditions.

Why the pupal stage matters

While not a feeding stage, the pupa is critical for completing the mosquito life cycle. It’s also a moment of vulnerability: although tumblers can dive to escape threats, they are less agile than larvae and cannot flee long distances. From a control perspective, this stage is harder to target. Since pupae don’t eat, biological larvicides that rely on ingestion are ineffective. However, environmental interventions, such as removing standing water or introducing surface oils, can still be useful in preventing emergence.

In the next article, we’ll observe the adult mosquito break free from the pupal casing and take its first flight. This is a moment of transformation that sets the stage for both survival and, potentially, transmission.

Click here to read the entire series.