Tuesday, July 26, 2016

The OTHER clothes moths

This week I received reports of two insects that are sometimes confused with clothes moths or pantry pests. The brown house moth, Hofmannophila pseudospretella, is a common moth pest in the United Kingdom, but much less so in the U.S.  In a paper written in the 1950s, one researcher noted that it probably occurred in small numbers in every private home in Britain, and that few stores or warehouses in Britain were without at least a small population.  The brown house moth specimens I saw on a sticky card this week, however, were the first ones of this moth I've ever encountered in Texas.

Brown house moth on sticky card.  Head to tail, these  
small moths are between 4 and 7 mm long. 
The BHM could easily be mistaken for Indian meal moth based on size.  But wing patterns are different.  Wings are bronzy brown with dark flecks on the forewings.  It is a slow grower with about one generation per year, but capable of becoming abundant under the right conditions.  It appears to require high relative humidity of 80% or more, perhaps accounting for the fact that it is not so common in climate controlled homes here in the U.S.

The diet of BHM is varied, ranging from cereal products to wool and dead insects.  It is readily capable of developing in wheat germ, whole wheat, damaged beans, macaroni, fish meal.  When yeasts were present, it could also develop on feathers and flannel wool.

Woodroofe, a British entomologist who studied the moth over 60 years ago, felt that the importance of this moth in homes was more as a fabric pest than a pest of stored grains.  If this moth is found in a home the most likely source of infestation would likely be in a basement or garage with higher humidity.  Check for pet food, woolen clothing, furs or feathers being stored under damp conditions. Also look in light fixtures with dead insect accumulations, or old bird nests in chimneys or soffits. Sticky traps may be useful in catching some of the moths for identification. If the suspected site of infestation is in an inaccessible void, consider dusting the area with Cimexa or Tri-Die, or other dessicant dust. If given a chance, these little moths can become very abundant.

Household casebearer cases collected from a
home in east Texas.  Note the caterpillar head
emerging from the case on the far right, and the
flattened cases widest in the middle. Photo by
Randy Reeves.
Another interesting insect that I encounter more frequently in samples is the plaster bagworm or household casebearer, Phereoeca uterella.  A close cousin to the clothes moth, household casebearers live inside a spindle-shaped silken case.  University of Florida provides a nice article on this moth, which feeds largely on spider webs.  If that sounds like an odd thing to eat, remember that spider webs are a type of proteinaceous silk, and probably just as nourishing to a clothes moth as silk clothing made from silkworm silk.

Like the BHM, household casebearers thrive in higher humidity conditions.  The cases, like a silk purse, are usually flat in later life stages.  It is most likely to be confused with the casemaking clothes moth, a more frequently encountered pest; but the spindle shape, and flattened case are distinctive.  According to the Florida fact sheet these cases may be found "under spiderwebs, in bathrooms, bedrooms and garages... on wool rugs and wool carpets, hanging on curtains, or underneath buildings, hanging from subflooring, joists, sills and foundations; on the exterior of buildings in shaded places, under farm sheds, under lawn furniture, on stored farm machinery and on tree trunks."  Besides spider silk, the caterpillars have been observed to feed on wool, human hair and dead insects.

I've not heard of any infestations severe enough to require insecticide use with household casebearer. In most cases they seem to be a curiosity more than anything; but a vacuum cleaner to get rid of spider webs would be a good idea to make sure that your casebearers don't decide to nosh on something a little more valuable in the home.

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