[Insect Identification] A Pest to Challenge the Sleuthing Skills of Sherlock Holmes

One of the nicest things about being an extension entomologist is getting to hear what’s going on in the world of pest control without the hard work of following you around. Specifically, I get to hear stories about you from your customers. A recent call had to do with a not-too-common insect that puzzled several of you recently and had me donning my Sherlock Holmes cap.

A new homeowner was experiencing an invasion of little larvae in her living room, near a fireplace with no food or obvious source of the critters nearby. I had about a dozen specimens in hand, the number that the caller and her husband reported seeing every day for the past several weeks. At least three PMPs examined the insects; one determined they were “maggots”, another suggested old house borers (the people were finding a dozen or so each day on their hardwood floors), and another had no clue. (A photo of the culprit appears at left.) What would be your best guess? Since this wasn’t a no-brainer for me either, bear with me as I share my thought process used to determine the identity of these insects. As you read, see if you can guess the final diagnosis.

ENTOMOLOGICAL MYSTERY. Like a garage mechanic trying to diagnose an old car, entomologists commonly use the process of elimination and deductive reasoning to explain strange insect problems — of which this industry sees a lot. My sample was certainly an insect, because it had six legs, but fly maggots (say from a carcass) were out of the question because fly larvae are legless. At first glance, these little guys reminded me of the Indian meal moth, the most common similar-sized larva found in similar situations. But my insects did not have prolegs (the fleshy claspers found on the abdominal segments of moth and butterfly caterpillars). Because of their prominent legs, caterpillar-like shape, and lack of prolegs I knew they were some type of beetle. I also immediately knew they could not be old house borers or any kind of wood-boring beetle because insects that live in wood are usually white and their legs tend to be microscopic — very small, if present at all (legs aren’t very useful for inching through dark, narrow galleries in the wood). Also, wood borers never leave their safe galleries during the larval life stage. Insects emerging from stored products are always prime suspects in these type of cases. Although they slightly resembled hide beetles, they lacked the hairy bodies associated with dermestid larvae. I knew from experience that they did not look like the larva of any other common stored product pests.

So Watson, where does that leave us? Could the beetles have sneaked indoors around a crack in a window frame or under a door? Probably not. There were too many of them to be coincidence, and this is not a common behavior for outdoor, plant-feeding or carnivorous beetles. If, in fact, they originated in the house, that left me with two likely remaining sources: 1) They could be some kind of decomposer insect that feeds on dead animals or decaying plant materials; or 2) they could be an insect that lives in the nests of other animals. With a fireplace nearby either choice seemed likely.

Any guesses? The only obvious, distinctive physical characteristic on these relatively plain beetles were two sets of hooked, horn-like structures on the last segment of the abdomen. At this point a little entomology experience saved a bunch of research time — that, and a quick call to the Texas A&M University entomology museum assistant curator, Ed Riley. Ed and I both had a suspicion but needed a picture to confirm it. We Googled “hive beetle” and, sure enough, at a University-based Web site (my first choice when faced with hundreds of hits from Google) we saw our culprit.

MYSTERY SOLVED. The small hive beetle, Aethina tumida, is a relatively new structural pest in this country. It’s really not considered a structural pest, but a pest of bee hives, where it feeds on bee larvae in their waxen nurseries. I have encountered the adult form of this beetle from samples taken in homes before, but never the larva. I suspect that our industry will see more and more of them over time.

My conclusion? The new homeowners had not yet discovered that along with their new home they had also purchased a bee hive, hidden perhaps in a wall or ceiling area. The hive beetles were the only evidence they had seen of this hive, but as Sherlock Holmes could tell you, the evidence never lies.

These kinds of challenges keep our profession interesting and fun. Perhaps it’s no coincidence that when Sherlock Holmes retired, he took up beekeeping as his choice of amusement.

The author has been an entomology specialist for Texas AgriLife Extension since 1989. Contact him via e-mail at mmerchant@giemedia.com.