Bad Bugs: Clothes Moths

By Alain VanRyckeghem, BCE
Technical Director

Identification: Webbing clothes moths (WCM) Tineola bisselliella are the most common of the moths attacking stored materials containing feathers, wool, or hair. It has a uniform shiny gold color with a reddish orange tuft of hairs on the head. The casemaking
clothes moth (CMCM) Tinea pellionella is less common and appears as uniform silvery
grey to shiny light brown, with dark grayish hairs on the top of the head and often with a small dot in the middle of the forewings. Both moths are similar in size, about 5–6 mm (3/16”) head to wingtip.

Life Cycle: The typical time to complete the life cycles for these moths can be in the 5–12 week range under optimum conditions, but as long as 16 weeks to a couple of years under adverse conditions. The WCM favors a warm environment with relative humidity (RH) in the 70% range, but can tolerate RH to 30%. The CMCM develops faster in higher RH, near 90%, and prefers cooler temperatures. The optimum temperature for WCM is 84–87° F while CMCM prefer 74–77°F. Adult WCM will live for up to 4 weeks, whereas the CMCM will only live for a week.

Biology and Behavior: Webbing clothes moths are most active indoors from April to November. They may also be caught in traps near the exterior of homes (see article about outdoor trapping of WCM). In well heated homes these moths can be caught in monitoring traps in the winter months as well. In December 2011, our room temperature lab cultures had more than 10,000 WCM in larval form and about 30% emerged as adults for the Christmas celebrations! Unlike CMCM we do not see the WCM having any significant natural breeding habitat outside of human habitation. CMCM can often be found in small nests of birds or in unheated buildings with bird activity or farm animals.

Webbing clothes moths are reluctant to fly, especially females, if located in storage areas with edible garments or antique materials with feather, hair, fur, or with woolen floor coverings. They run very quickly when disturbed and hide from bright lights. The
cream colored larvae have brown head capsules and freely run around the infested materials, sometimes within silken tunnels. They usually produce white pupae on the infested material; leaving damage that resembles granular pepper and short trails of webbing.

Case-making clothes moths are considered excellent fliers and can easily move about a structure looking for new harborage sites in ideal temperature and humidity zones. The larvae have black head capsules and travel about within a case of woven material that often contains the colored threads of the infested article. Damage is similar to WCM except that there will be no streaks of webbing and often the pupation may be away from the site of infestation, perhaps on a wall or a ceiling.

Monitoring and Control: The behavior of the two moths dictates the proper choice of trap and lure. Webbing clothes moths prefer to hop and jump into a trap, with a three pheromone blend lure, sitting on a shelf, a cabinet, or floor, in a drawer or under
furniture. The CMCM prefers to fly into a trap rather than land and walk into it. Hanging traps with a single pheromone lure is the best choice for this moth. While there can be some cross attraction to the lures by each moth, research has shown that best results are achieved when using the proper lure for the moth species present.

Control of these pests requires considerable effort on the part of the home owner or commercial client. Moth traps can capture lots of moths, but like food moth infestations, if the source of the moths (larvae) is not removed, treated or frozen, then the traps continue to harvest moths, while the damage caused by larvae continues to grow. Some structural
treatment of the home or building and floor coverings can help reduce the activity, but a careful examination of the wardrobe and storage rooms/closets is necessary to find the hidden infestations.