Running from Little Brown Moths

Little brown moths, like this meal moth,
Pyralis farinalis, can pose an identification
challenge to untrained PMPs.

Skill at insect identification is one of the little things that distinguishes the well-trained from the not-so-well trained pest control technician. And one of the pest problems that stop many a technician in their tracks is the so-called, "little brown moth".  Even entomologists are disposed to run the other way when a little brown moth shows up--so much so that bug experts often use the acronym LBM when sorting these insects from other, more interesting creatures.

But it's really not fair to the moths, or your customers, to give up so quickly on little brown moth identification--especially when the moth is an indoor pest. Household moths are pretty distinctive when examined carefully, and with a little practice identification decisions about indoor moths are not that difficult to sort out.

First a little background.  Moths, along with butterflies, are insects in the Order Lepidoptera--one of the largest insect groups, with almost 175,000 known species. Perhaps the most distinctive lepidopterous feature is the membranous wing surface covered with flattened, modified hairs, called scales.  Scales are what give each species of moth or butterfly their distinctive body and wing color pattern. 

All Lepidoptera go through a complete metamorphosis as they develop.  This metamorphosis starts out with the egg and larval, or caterpillar stage.  After the caterpillar is fully developed there is a pupal stage, then the adult emerges. In moths, it is typically the caterpillar stage that causes the most damage to plants or to stored products; although in pest control the adult stage flying indoors can also be a problem. 

The most common indoor pantry
pest is the Indian meal moth, shown
here resting in its characteristic
push-up position.

Your first job when faced with an indoor LBM problem is to determine the source. Is the moth coming indoors from outside, or is there an indoor source of the infestation?  And secondly, is this a food-infesting pest, or is it a clothes moth?  The first question can be answered to some extent by considering the numbers of moths present (outdoor moths should not be common indoors), but also by familiarity with the important indoor moth pests.  The second question is answered by familiarity with the appearance and behavior of the two major species of clothes moths.

Comparison of sizes and wing
shapes of Indian meal moth (top),
Angoumois grain moth, and
clothes moth (bottom).

The most common types of moths found in residential or commercial interiors are pyralid moths. Pyralid moths include the Indian meal moth, Mediterranean flour moth, almond moth, raisin moth and others. These moths all have a relatively short fringe of hairs on the hind wing.  The Angoumois grain moth is a smaller moth with a 1/2 inch (13 mm) wingspan and a long fringe of hairs on its hind wings shaped like a pointing finger (see right).

Clothes moths are the smallest of the moths likely to be found indoors (3/8-inch or 5-7 mm wingspan). They are covered with light brown to golden scales and have a tuft of hairs on the forehead. The hind wings lack a pointing finger shape. Clothes moths do not readily fly, and prefer to scuttle or run. For this reason, clothes moths can usually be ruled out as the culprit when a client reports seeing flying moths commonly indoors.

If in doubt as to the source of an indoor moth problem, pheromone lures can help. Pheromone lures contain copies of the sex pheromones that these moths use to locate mates. Pheromone lures can be placed throughout an account to help pinpoint moth hot spots. Some pheromone formulations for moths are even available as confusing agents to prevent males from finding female hosts (this approach is not effective for clothes moths, as explained in an interesting article just out in Fumigants and Pheromones newsletter).  Pheromone traps are available for many species and Insects Limited is an excellent source for information on selection and technical aspects of pheromone use.  Another commercial source for pheromones is Trécé Inc.

For anyone with deeper interests in stored product pest identification, including detailed keys to stored product pests, an excellent resource is the USDA Agriculture Handbook 655, Insect and Mite Pests in Food, now accessible online.

With all the great resources available there really is little reason to run from those Little Brown Moths.