Mecoptera belong to the Kingdom of Animals, the Phylum of Arthropoda, the class of Insects and the Order of Mecoptera (Scorpion flies, Hangingflies, and Allies). This order of insects have about 550 species in nine families around the world. These insects live in moist, sylvan habitats and the larvae and adults are omnivorous. 

Mecoptera eggs will grow as the embryo grows within it. Sometimes they can grow up to 100%.

As larvae, they generally stay in the soil. They are generally cruciform or are like a caterpillar. They may have a modified form that is scarabeiform. This means that it is grub-like. They will have a well-developed head and a thick cylindrical body. They also have three pairs of thoracic legs, but they do not have prolegs. This form is the Boridae or Panorpidae.

Another way that they may be modified may be campodeiform. This modification give the larva an elongated and flattened boddy. They also hav well-developed legs and antennae. This is the Nanochoristidae.

As adults, their head are extended to a deflexed rostrum or a beak. The adults have biting mouthparts at the end of the head. The head is also not more broad than the front of the thorax. The head may be described as “horse-like”. The antennae are thread-like and have fourteen or more segments. Often the antennae are half of the body length, or they may be longer.

The front and back wings are similar in shape. In some of the Mecoptera, the wings may be absent or smaller in size. When wings are present, they will look mottled.

Mecoptera have compound eyes that are located on the side of the head. Their eyes are prominent and semi-globose. They have thirty or more ommatidia. Each ommatidia resembles one simple eye. There are also three ocelli, or small simple eyes with sensory cells and a single lens, located on the top of the head.

The body is typically soft and an elongated cylinder. Attached to the body are the tarsi divided into five segments. They are long and slender. Hangerflies have legs that have a single opposable claw at the tip of each. They use the front legs to hang from vegetation and the middle and back legs are used to catch small insects.

Scorpion flies get their names because the terminal segments of the male genitalia are enlarged and held curved over the abdomen, like a scorpion. The tail is harmless in these insects, though.