How to get rid of beetles in the kitchen?
Ten years ago, when returning from a vacation in Italy in July, there were several dark beetles on the white windowsill in my kitchen in my recently bought apartment, and they were identified by experts as Reesa vespulae. I got exterminators to fumigate the entire kitchen and I also threw out an old leather couch I had, since I read that this beetle eats dead animal matter and I was going to replace it anyway.
I got similar beetles once again 6-7 years ago, and again got exterminators. Now, I found the telltale "skins" in one of my kitchen drawers a few days ago and found a dead beetle in one cabinet after that. Yesterday saw the first live beetle in the kitchen windowsill, and today there were two. I'm going to get exterminators, but I wonder why these keep coming back.
After the two previous incidents I've been vigilant about cleaning and keeping everything in closed containers. The skins were in a drawer that contains no foodstuff and the dead beetle was in a cabinet with fancy porcelain, one that's rarely opened. Every description of this pest says that it lives on dead insects, museum material, various stored seeds and dried plant material. What could it be eating in my home?
The kitchen cabinets are from when the house was built in the 1980s. Could they be living in the wood between or behind the cabinets? It's a stone house, but the cabinets are wood. I'm starting to think there's something dead somewhere behind or underneath the cabinets and feeling totally grossed out. I'd most of all want to burn the entire kitchen down, but should I rip out the cabinets and the flooring (tile over original ancient linoleum, laid by previous owners) at this point, since repeated fumigations don't work? I live in one of the Nordic countries, so this beetle doesn't live outside. I don't think so, at least.
The Reesa vespulae beetle, and its fellow members of the Family Dermestidae, are frequent and ubiquitous pests of human dwellings. Unless your apartment was hermetically sealed, you cannot expect to keep these, or other household pests, from occasionally invading your living space. It sounds like you are a meticulous housekeeper but it is an impossible task to keep a home free of all possible food sources for this type of beetle. Dermestid beetles, including R. vespulae, also live outside in the warmer months and the adult beetles seek suitable food sources to lay eggs on or nearby, if they can't reach them physically.
The species that is giving you trouble is originally native to North America. Its natural habitats are wasp and bird nests but, it takes a wide range of suitable food and adapted well to human created habitats. Your beetles would not be originating from beneath the tile flooring. The possibility does exist of a dead mouse behind the cabinets. However. there would be no guarantee of mouse not dying behind newly installed cabinets in the future.
I think, in most cases, the windows on buildings are the initial entry point for dermestid beetles. Window casings have weep holes to allow drainage of rain water and almost always also have accumulation of dead insects in the drainage system and where the sash weights hang in the frames. Even if the window screening is tight enough to prevent the entry of the adult beetles, they will lay eggs that hatch. The tiny larvae can easily pass through window screens and cracks. That is why insect collection drawers are built so tight, to attempt to exclude them. I have a small 21,000 insect specimen collection that I curate and it is a constant battle to exclude the dermestid beetles. You should actually congratulate yourself about the infrequency of your encounters with these pests. Your high level of cleanliness will prevent these common household pests from being little more than an occasional nuisance.