Caddisfly head. Coloured scanning electron micrograph (SEM) of the head of a caddisfly (order Trichoptera). At centre are the fly's mouthparts. It's mandibles (biting mouthparts), which are greatly reduced, are at lower centre, below these are the labial palps. At centre right and left are the maxillary palps. Both pairs of palps are sensory organs, covered in hairs. At right and left are the compound eyes (red), made up of many individual ommatidia (spheres). Adult caddisflies are short-lived moth-like insects. They have hairy wings, opposed to the scaly wings of moths and butterflies. The caddisfly larvae are aquatic. The adults hatch en masse, creating great swarms over lakes and rivers that attract fish. Due to this caddisflies are often used as bait by fishermen.