Although there are several possibilities, the potential of a stored product pest infestation should not be overlooked-in particular, the presence of flour beetles.
The confused flour beetle and the red flour beetle look very similar in appearance. The best way to distinguish the two is by examining their antennae. The RFB's antennae take on a clubbed shape with three segments at the end, while the CFB's antennae gradually enlarge towards the tip, ending in a four-segmented club.
Another difference between the two beetles is that the RFB (primarily found in southern states) is a strong flier, while the CFB (primarily a northern pest) does not fly.
As adults, both beetles have shiny, reddish brown bodies that are about 1/8 inch long, flattened, and oval. They have a very wide food range including flour, rice, cereals, grains, spices, grain products, shelled nuts, dried fruit, chocolate, beans and other similar materials.
Average life span of both the confused and red flour beetle is between 1 and 3.5 years. They have four life cycle stages, which include the egg, larvae, pupae and adult. It's important to note that all four stages of the life cycle may be found in infested grain products at the same time.
When female beetles of either species lay their small, white eggs, they do so in flour or other food material. The eggs, which are coated with a sticky secretion, become covered with the product and easily stick to the sides of sacks, boxes, and other containers.
In the larvae stage, both species are small, slender, and worm-like in appearance. When fully grown, the larva is 3/16 inch long and white, tinged with yellow.
As confused flour and red flour beetles transform into a small pupa, they gradually change from white, to yellow, and then brown. Shortly after turning brown in color, they transform into an adult beetle.
So now that we've identified the pest, the next question is:
Why is a pest that feeds on flour, rice, and other grain products in my bathroom instead of my kitchen?
The answer to the above question is very easy- you have a food source in your bathroom.
To eliminate the pest problem, you just have to remove the food source. Thoroughly inspect your cabinets, drawers, and closets for rodent poisons, septic system treatments (powder or flake form), hidden pet treats, rice bag heating pads, prescription drugs, etc. It can be a frustrating task, but with a little persistence, you should be able to locate the source of your problem.