Description

• Periwinkles look similar to caterpillars. They can grow up to 1 1/2 inches in length. Their bodies range in color from yellowish-green to brown. Periwinkles may have very small antennae or none at all. Six legs are on the upper middle section of the periwinkle's body. Two fleshy extensions with small hooks on the tip, known as prolegs, are attached at the end of the body. Periwinkles curl into a C shape when placed on a flat surface.
  
  

Life Cycle

• Adult female caddisflies lay eggs in freshwater, on aquatic plants or at the shoreline. As soon as the eggs hatch, the larvae start collecting materials and constructing shells. Periwinkles secrete a sticky substance from their mouth to glue twigs, leaves, pebbles or any other small materials to their bodies to form a case. Caddisfly larvae retreat into the case when threatened. The larvae stage lasts from a few months and a year. When the larvae are finished growing, they seal up the opening to their case and spin a cocoon to pupate. Afterward, adult caddisflies emerge and fly away to mate.
  
  

Food Source

• Periwinkle bugs have chewing mouth parts and generally feed during the day. They feed on anything they find on the bottom of the body of water where they are living. Periwinkles will consume decaying organic material, algae, fungi, aquatic vegetation and even small insects. They sometimes spin silk and make a net to catch food.
  
  

Management

• Pest control is usually not needed for periwinkles because they do not cause damage to their environment. Several natural predators, such as crayfish and other aquatic insects, are attracted to periwinkle bugs. Birds, bats, frogs, spiders and other creatures eat adult caddisflies. Since many caddisflies hatch simultaneously, large numbers of predators are attracted to the area. Most caddisflies will be eaten by predators, according to the Fairfax County Public Schools webpage.