Mosquitoes are dipteran insects measuring up to a centimetre long. Their body consists of the head (cephalon), thorax, and abdomen. The head includes a pair of compound eyes, a pair of antennae, and a piercing-sucking mouthparts. The antennae are characteristic of the suborder Nematocera and comprise numerous identical segments. The piercing-sucking mouthpart consists of an unpaired upper lip (labrum), a grooved lower lip (labium, formed by fused maxillae II), an unpaired hypopharynx, a pair of mandibles, and a pair of maxillae I. The grooved labium forms a sheath for the proboscis, which folds back upon piercing the skin and does not enter the wound. The sharp, serrated maxillae I cut into the skin, while the mandibles keep the incision open. The labrum acts as a sensor to locate capillaries and together with hypopharynx forms a tube called the proboscis. Proboscis delivers saliva to the wound and extracts blood. The saliva prevents blood clotting and acts as a lubricant for the piercing structures.

The three-segmented thorax is highly centralised, meaning the central thoracic segment (mesothorax) is the largest. Each thoracic segment has a pair of segmented legs. Additionally, the mesothorax features a pair of sparsely veined wings, while the posterior thoracic segment (metathorax) contains a pair of small, modified wings called halteres. These generate buzzing sounds and act as mechanoreceptors, aiding in balance and flight stabilisation.

Mosquitoes are holometabolous insects, meaning they undergo complete metamorphosis. Their life cycle begins with eggs, which females lay up to 300 in water. Most mosquitos are not picky about the type of water body they lay their eggs in. The eggs hatch into larvae, which consist of a head, a legless thorax, and an abdomen ending in a respiratory complex with gills and a siphon for atmospheric oxygen intake. After several moults, the larva pupates. Pupae are aquatic, can move and breathe through respiratory horns. After 24-48 hours, the pupae transform into adult mosquitoes. The entire development takes between one week and nine months, depending on the species. Different species exhibit overwintering or summer dormancy to survive unfavourable conditions, either as eggs or blood-feeding females.

Mosquitoes are well-known for feeding on blood, but only females do so, which is essential for egg production. Due to their blood-feeding habits, they are vectors for numerous diseases. The mosquito species composition in Slovenia is changing, with tropical species becoming increasingly common.