Snakefly

Snakeflies belong to the order Raphidioptera. The name comes from Ancient Greek words meaning "needle" and "wing."

There are approximately 260 living species today. These insects are divided into two families: Raphidiidae and Inocelliidae. They are predatory insects, which means they hunt other creatures for food. Most snakeflies live in temperate regions of the world. However, they are not found in the tropics or the Southern Hemisphere.

An adult snakefly has a very distinct body shape. It has a long and slender body. The insect possesses two pairs of long, membranous wings. These wings have a primitive venation pattern, which refers to the arrangement of veins. They also feature a colored wingspot called a pterostigma.

The most recognizable feature is the elongated prothorax. The prothorax is the first segment of the thorax behind the head. This long segment allows the head to be very mobile. This movement is why people call them snakeflies. The head is often flattened and heavily sclerotised, meaning it is hardened.

Scientists distinguish the two families by looking at specific traits. Members of the family Raphidiidae have three distinct ocelli. Ocelli are simple eyes used for sensing light. In contrast, members of the Inocelliidae family have no ocelli at all. You can also tell them apart by looking at the pterostigma. Inocelliids lack a specific cross vein in this wingspot that Raphidiids possess. Both families have females with a large, sturdy ovipositor. An ovipositor is a specialized organ used to deposit eggs. They use it to place eggs in crevices or under tree bark.

Snakeflies are holometabolous insects. This means they undergo a four-stage life cycle consisting of eggs, larvae, pupae, and adults.

The eggs hatch into larvae within a few days to three weeks. The larvae have large heads and projecting mandibles, which are biting mouthparts. While their heads are hard, the rest of their bodies are soft and fleshy. They do not have prolegs, but they do have an adhesive organ on their abdomen. This organ helps them fasten themselves to vertical surfaces. The larval stage can last for a long time. Some species stay as larvae for two to three years, while others can last six years.

Metamorphosis requires specific environmental conditions. All snakeflies need a period of cool temperatures to induce pupation. This chilling process is necessary to move from the larval stage to the pupal stage. Most species pupate in the spring or early summer. This stage usually lasts from a few days to three weeks. If a larva begins pupating in late summer, it may take ten months to emerge as an adult. In laboratory settings, insects kept at constant temperatures can become "prothetelous." These insects develop adult features like compound eyes but live for years without finishing metamorphosis.

Snakeflies have a very ancient evolutionary history. They first appeared during the Early Jurassic period. They reached their peak of diversity during the Cretaceous period. However, an enormous asteroid likely hit Earth 66 million years ago. This event is known as the Cretaceous–Paleogene extinction event. This catastrophe likely wiped out most snakefly families. It specifically extinguished tropical and sub-tropical species. Only the most cold-tolerant species survived. Because modern snakeflies closely resemble those from 140 million years ago, they are often called living fossils.

These insects play an important role in their ecosystems as predators. Both adults and larvae eat soft-bodied arthropods. Adults are diurnal, meaning they are active during the day. They are important predators of mites and aphids.

Larvae live in places like tree bark, leaf litter, or rock crevices. They eat the eggs and larvae of spiders, barklice, and springtails. Because they eat agricultural pests, some people have considered them for biological control. However, they grow their populations very slowly. This makes them difficult to use for farming. Additionally, they face many predators, such as woodpeckers and nuthatches.