Beneath the surface, mosquito larvae are already preparing for life in the air. Once the mosquito egg hatches, a new stage begins; one that is aquatic, active, and essential for development. The mosquito larva emerges into its watery world equipped with the ability to move, grow, and feed. Although not yet capable of flight or biting, larvae are highly vulnerable and play a crucial role in the life cycle of the malaria vector. For the Anopheles mosquito, this stage also sets the stage for what comes next: transformation into a pupating insect and, eventually, a flying adult.

Life in four instars

Mosquito larvae go through four distinct growth stages, known as instars. Each instar marks a phase of development between successive moults, where the larva sheds its outer cuticle to grow. These stages are referred to as first, second, third, and fourth instar larvae. After hatching, the mosquito enters the first instar stage. At this point, the larva is very small, delicate, and highly vulnerable to environmental threats. As it grows, it progresses through the second and third instars, during which it becomes noticeably larger, more mobile, and increasingly active in its aquatic environment. Finally, it reaches the fourth instar, the largest and most robust larval stage, during which it prepares for the next phase of development namely pupation. Each instar lasts about one day under optimal conditions, meaning the entire larval stage typically spans 4 to 7 days, depending on temperature and food availability. Cooler climates may extend the duration, while warmer, nutrient-rich environments speed it up.

Feeding, breathing, moving and shaking

Larvae are filter feeders. They consume microorganisms, algae, organic debris, and bacteria suspended in the water. Constant movement of their mouth brushes helps sweep food particles toward their mouths. Unlike fish or other aquatic animals, mosquito larvae do not have gills. Instead, they breathe air through spiracles, small openings located near the tip of their abdomen. Anopheles larvae differ from most others in that they lie parallel to the water surface, rather than hanging vertically. This resting posture is a helpful identification feature in the field. To avoid suffocation, they must regularly return to the surface for air. This makes them vulnerable to surface oils or chemical agents that disrupt their ability to breathe.

Mosquito larvae are surprisingly mobile. They swim by jerking their bodies in an S-shaped wriggling motion, and they are often fondly known by their nickname “wrigglers.” This motion allows them to escape predators and disturbances but also brings them into contact with food throughout their aquatic habitat. Despite this agility, larvae are prey to a wide range of predators including fish, aquatic insects, and birds. Natural predators can be valuable allies in integrated mosquito control strategies.

Why the larval stage matters

From an ecological standpoint, larvae serve as food for other organisms and help break down organic material in water. But in the context of public health, their presence signals an opportunity for intervention. Because mosquito larvae remain in confined aquatic environments and cannot yet fly, larval control is often easier than trying to track adult mosquitoes. Targeted larviciding, habitat modification, or introducing larvivorous fish can all reduce mosquito populations before they ever reach adulthood. When the final moult occurs, the larva transforms into a pupa, marking the beginning of a silent, non-feeding phase.

In the next article, we explore the next transitional stage: the pupa, where the wriggler stops feeding, and metamorphosis begins.

Click here to read the entire series.