A cocoon is a protective casing, usually made of silk. This casing protects the larval, or immature stage, of an insect from the elements, such as extreme temperatures. Inside the cocoon, the larva, which is often wormlike, will undergo metamorphosis and emerge as an adult, a process common among insects and other arthropods.

4 Types of Pests That Build Cocoons

Cocoon-Building Insects

1. Fleas

Adult fleas, which pet owners may see on their dogs and cats, can lay up to 50 eggs a day. After hatching, these eggs produce worm-like larvae. Inside the home, these larvae may be found in carpet or other areas frequented by pets. The larvae form cocoons, and in 2-4 weeks will transform into adult fleas. These cocoons are nearly impossible to see.

2. Butterflies and Moths

Butterflies and moths are perhaps the most commonly known insects that build cocoons. Their larvae, which are caterpillars, are voracious eaters. Caterpillars spin silk, and this silk is used to form the cocoon for the pupal stage of development – the final stage before adulthood. Some moths, such as the clothes moth, may find their way into homes. These moths feed on common household items, such as fibers in clothes and grains or other foods in the kitchen. If necessary, these moths may form cocoons and pupate in your house. A pest control professional can help identify the cocoon and the species of moth that created it.

3. Caddisflies

Some species of caddisflies build cocoons. These insects resemble moths, and they spend most of their lives in or near bodies of water like lakes, rivers and ponds. The larval stage of these insects lasts up to two years, during which they feed on algae or other small organisms found in the water in which they live. Larval caddisflies spin silk and use this material to make cocoons or casings around twigs and other particles in the water, like sand and gravel. Typically, caddisflies pupate from the winter through the early spring.

4. Parasitic Wasps

Some species of parasitic wasps attack hosts and use these host insects as nutrients for their young throughout development. The stage at which the wasp attacks varies with species, some attacking eggs, others choosing larvae or adults. Common host insects include aphids, caterpillars, sawflies, beetles and flies. After larval wasps have emerged from their eggs within their hosts, they spin silk to form cocoons either inside, around or nearby their hosts.

Identifying Pest Cocoons

As with any pest, it’s important that you know exactly what you’re dealing with in order to determine the right course of treatment. Properly identifying pest cocoons can be tricky, and depending on the insect, attempting treatment yourself may be ineffective or even risky. Some of the pests mentioned above can be found in your home. Others, like caddisflies and parastic wasps aren't likely to be found in your home. However, these should be treated professionally, and some may even attack and sting when they feel threatened.

If you think you have spotted cocoons in or around your home, or want to help avoid an infestation in the first place, contact Terminix® for a solution.


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