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Cockroach Nymphs Leave Their Shed Skins Behind

By Chris Williams on July 9, 2014.

We just moved into a new apartment in south Boston that I think used to have a cockroach problem. In some of the cabinets, I’ve found these light brown, crispy-looking shells. They’re smaller than a cockroach but they have kind of that same shape. Are these dead cockroaches?-BP, Boston, MA

Blattidae cockroach skinNymphs Have to Molt in Order to Grow

You’re probably seeing not dead cockroaches, but the shed skins (called exuviae) that are left behind when cockroach nymphs molt. I say cockroach nymphs because adult cockroaches don’t molt. Molting or shedding its skin periodically is the only way that a young cockroach can grow since its hard, outer cuticle won’t allow expansion. The process of molting is called ecdysis.

When a cockroach nymph has outgrown its old skin, it finds a protected place to complete the molting process. It takes in air and splits its old skin right down the back. It then painstakingly has to pull its body, including 6 legs and antennae, out of the old skin. Sometimes the nymph is not successful and dies, or is eaten during the molting process. Once out of its old skin, the now white and soft cockroach nymph remains hidden and inactive for several hours while its new cuticle hardens and darkens (see “’White Cockroaches’ Have Just Molted”).

The number of molts that each cockroach nymph goes through varies depending on the type of cockroach. The entire nymphal stage for a German cockroach nymph (our most common cockroach) usually lasts 55-68 days, depending on conditions like temperature and available food. During that time, the wingless nymph will molt 6 or 7 times before turning into an adult cockroach. At that final, seventh molt, the adult cockroach emerges with wings for the first time, and with functional reproductive organs.

Shed Skins Mean Cockroaches Were Here

Seeing shed cockroach skins is always a sign of a cockroach infestation. However, the skins may be from a previous infestation that is no longer active. Often, cockroaches will eat the shed skins since they supply nutrients. It’s important when trying to control cockroaches that you clean up any evidence of cockroaches like shed skins, egg cases, dead cockroaches, and cockroach feces. Then, new evidence will be an indication of a new or ongoing cockroach infestation. Talk to your pest control technician about when to do this cleaning; you don’t want to wash off any treatment that has been applied.

Professional exterminators often use insect growth regulators (IGRs) as part of their cockroach control arsenal. These chemicals interfere with the growth and development of cockroaches, preventing nymphs from molting into reproductive adults. If you see live cockroaches or any sign of a cockroach infestation in your apartment, give Colonial Pest a call.

Photo credit: dhobern / Foter / Creative Commons Attribution 2.0 Generic (CC BY 2.0)

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