One of the best parts of my job is that I get to help coworkers with their problem accounts.  Sometimes it can be frustrating when a solution doesn’t clearly present itself, but when we are able to put our heads together and figure out how to solve a difficult problem it is extremely satisfying.  It can also be a tremendous learning experience.

Carpet beetle larva (left) and adult (right)

One day I received a call from a technician about a carpet beetle infestation.  A long time pest customer kept finding adult carpet beetles on the middle of her kitchen floor.  Carpet beetles are extremely common insects that seem to get in almost everyone’s home.  They are some of the great recyclers of the insect world as they feed on animal hair, dry skin, and dead insects.  It’s actually the carpet beetle larvae (which look like tiny short fuzzy caterpillars) that feed on these items and they can become pests when they target clothing, throw rugs, and furniture made with animal hair and other products.  They can be huge pests in museums when they attack stuffed animals or, *gasp*, insect collections.   Once they turn into adults (which are tiny mottled colored round beetles) they only feed on pollen and nectar from flowers.  When adult beetles are noticed in homes they are usually found dead on window sills after unsuccessfully attempting to get outside.  So, when adult carpet beetles were constantly found crawling across the kitchen floor it sounded a bit odd.

I met the technician at the customer’s house and we proceeded to do a thorough inspection to try and figure out the cause of the infestation.  We focused mainly on the surrounding areas of the kitchen, searching through cabinets and drawers to see if we could find the food source.  The house was immaculately clean, and no items made of animal materials could be found nearby.  There was a throw rug in the kitchen but it was made of all synthetic materials.  Next to the kitchen was the laundry room and we searched under and around the washer and dryer for potential food sources such as accumulations of lint from wool clothing.  The customer did have a small dog and the dog’s food and water dish were located in the laundry room but no beetles were found in the area.   On the floor of the kitchen, close to where the beetles were found, was a vent for the A/C system.  I removed the vent cover and felt around inside the duct and pulled out handfuls of debris, including lots of pet hair that had accumulated there.  In the debris were some cast skins from carpet beetle larvae, but no live house beetles.  I surmised that perhaps there was more accumulated pet hair deep in the duct work which could be the source of the infestation and suggested that the customer hire someone to clean out the ductwork.   She agreed and we left that day feeling somewhat convinced that we had resolved the issue.

The celebration was short lived however, when she called back a few days later and said she had her ductwork professionally cleaned but the beetle activity had not improved.  So, we went back to the house with hats in hand to try and figure out what we had missed.  Since we could not find the source nearby, perhaps it was located somewhere above or below.  Above was the second story of the house and there were no vents or lights or other potential entryways in the ceiling above the area where the beetles were being found.  Time to go below.  I pulled on a crawl suit, grabbed my flashlight and dove into the crawlspace.  I worked my way to the area below the kitchen and immediately noticed two things: lots of dead carpet beetle adults and lots of rodent droppings.  I pulled back the insulation and found lots more droppings.  Still, I could not find the food source for the carpet beetles but knowing there was a previous rodent infestation was important.  I exited the crawlspace, cleaned up, and went back inside to talk with the customer.  I asked if they had a rodent issue at some point.  She explained that a couple of years ago they were seeing rats in the house and we had resolved that issue.  The service technician remembered that and said he had used rodent bait in the crawlspace at that time but no bait has been present since the rats were eliminated.  In my best Sherlock Holmes impersonation (which is just my normal voice) I explained my theory that perhaps one of the rats had crawled into the void under the false cabinet bottom in the kitchen and died.  Carpet beetle larvae will feed on the dried remains of dead animals.  After exclaiming, “Oh my God you think there’s a dead rat under my cabinets?!” the customer agreed to let us remove the facing on the front of the cabinet bottom to see if my theory was correct.

Upon removal we quickly realized my theory was wrong.  There wasn’t a dead rat, but a large pile of old dry dog food and about a ½ inch layer of shed skins from carpet beetle larvae covering the floor under the cabinet along with thousands of larvae and adults scurrying about.  Apparently a rat from the rodent problem years ago had stolen dog food out of the dish in the laundry room and stock piled it under the kitchen cabinet and it eventually became infested with carpet beetles.  This was a learning experience for me because I didn’t know that carpet beetle larvae will occasionally attack old dry dog food that contains keratin, the same protein found in hair and skin that they feed on.  While my dead rat theory wasn’t exactly accurate, at least I was right about the location of the food source and I felt pretty good about that.  We cleaned out and disposed of the old dog food and carpet beetles, treated the surrounding area with insecticides for the stragglers and made our customer happy because we found a solution to the problem.  I felt pretty good about that too.

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