Mosquito larvae are the second stage in the mosquito life cycle, following the egg and preceding the pupa. These aquatic forms are often called “wigglers” due to their movement. They are commonly found in still or stagnant water sources such as bird baths, puddles, or neglected containers. Recognizing their unique physical structure and characteristic behavior at the water’s surface helps distinguish them from other aquatic life.
Physical Characteristics of Mosquito Larvae
Mosquito larvae range in size from less than 1/4 inch to over 1/2 inch long by their final stage, depending on the species. They possess an elongated, worm-like appearance with a body divided into a head, a thorax, and a segmented abdomen. The thorax is wider and appears somewhat globular, while the abdomen is narrow and segmented.
The color of the larvae can vary significantly, often appearing translucent, whitish-gray, or sometimes brown, influenced by their diet of algae, bacteria, and organic debris. A distinct feature is the siphon, a tube-like structure located near the end of the abdomen. This siphon functions like a snorkel, allowing the larva to access atmospheric oxygen. Most larvae must periodically push this siphon through the water’s surface film to breathe.
Movement and Breathing Habits
The larvae must regularly maintain contact with the water surface to survive. They hang suspended just below the surface, with their head facing downward and their siphon breaking the surface tension of the water. This position allows them to feed on microorganisms while simultaneously taking in air.
When disturbed by a sudden shadow or vibration, the larva detaches its siphon and rapidly swims downward with a jerky, C-shaped motion. Once the perceived threat passes, they must return to the surface to re-establish contact with the air via their siphon. This cycle of hanging and diving is a visual cue.
Identifying Larvae vs. Pupae and Other Aquatic Insects
Distinguishing larvae from the next stage, the pupae, and from other common aquatic insects is important. Mosquito pupae, often called “tumblers,” are non-feeding and have a different appearance. They are comma-shaped, with a fused head and thorax forming a rounded section and a curled abdomen tucked beneath.
Unlike the larvae’s siphon, pupae breathe through a pair of horn-like structures called respiratory trumpets. Their movement is also distinct; when disturbed, they tumble or flip through the water with a jerky motion. Larvae are sometimes confused with midge larvae, which are also worm-like but lack the prominent respiratory siphon. The phantom midge larva is nearly transparent and lacks a siphon, instead using internal air sacs for buoyancy, exhibiting a different type of movement and remaining fully submerged.