You may have never seen a mecopteran, such as a scorpionfly or a hangingfly, because the adults are so secretive. They hide out in dark, shaded woodlands. They don't fly much, spending most of their time sitting on leaves. Mating tends to occur at night. Mecopterans actually live all over the world, even in polar habitats. They prefer moist, shady conditions, like what you find in dense forests. Females lay eggs under damp leaves or soil on the forest floor, and the larvae develop in the dark hiding places. In polar areas, larvae may develop in clumps of moss surrounded by snow. Mecopterans are closely related to fleas and flies. But, mecopterans are larger, often with long, clear wings patterned with dark veins. Their heads are long too, narrowing down to where their mouthparts (mandibles) attach. Despite the sinister appearance created by their long, thin faces, they do not bite or sting.

An insect has a brain, connected to bundles of nerves (ganglia) in each of its three body segments. Like us, they have sensory nerves that receive information from their environment and send it to the brain. Information comes from many types of touch receptors. Touch-sensitive hairs all over an insect's body are sensitive enough to detect vibrations in the air, such as from an approaching predator. Insect hairs also do chemical detection (chemoreception). Pores at the end of chemoreceptors on mouthparts or other body parts allow odors to reach the nervous system. Insect antennae may have thousands of chemoreceptors, used to detect chemicals in the air (pheromones) emitted by members of the opposite sex. An insect, like us, has a pair of eyes on its head. But, insect eyes are compound, with hundreds or thousands of lenses, together making an image consisting of spots of light, like pixels. An insect's sound receptors are on its legs.