The bugs that bug FDA inspectors the most – flour beetles; Food and Drug Administration; includes related article
Bugs That Bug FDA Inspectors the Most
One thing you can say about flour beetles: They know their nutrition. When they go after stored wheat, for example, they eat only the germ portion where all the nutrients are and leave behind the kernels.
And they’re clever in other ways. They have functional wings that they use judiciously, preferring not to expose themselves needlessly. They burrow down into flour so they cannot be seen and, with food particles clinging to the hair on their little (one-seventh of an inch long) bodies, look just like what they are hiding in. Even their eggs have a sticky surface that catches food particles, adding to their camouflage.
And are those beetles ever mean. If they find that a food they want is already claimed by other insects, they will drive out or destroy the home-steaders and take over the entire supply for themselves. In fact, macaroni is one of the few foods where the flour beetles’ competitors can survive: Smaller insects crawl inside the tubes of pasta where the beetles are too large to pursue them.
With traits like this, it’s no wonder they have survived since prehistoric times to be the most prevalent insect pest in our basic food supplies.
There are more than 150 different kinds of insects that infest food after it has been harvested, causing the loss of at least 10 percent of the world’s food supply every year, usually in developing countries that can least afford such losses. Flour beetles are the most abundant and destructive of these insects and are the insects most often found by FDA inspectors in food manufacturing plants and warehouses.
Wherever they are found, flour beetles cause serious damage. They prefer to eat flour and other grain products, such as bread, noodles and cereals, but they will also devour whole grains such as wheat, oats and barley. If no grain is available, almost any dry vegetable material will do. They have been known to infest nuts, beans, dried fruits, cocoa, yeast, spieces, tobacco and marijuana. They can even live and breed in the fiery and seemingly hostile environment of pure paprika.
Flour beetles even engage in chemical warfare. They give off noxious chemicals called quinones when they are disturbed or startled, to drive away predators or other competing insects.
Quinones are responsible for the characteristic musty odor of beetle-infested flour and can even affect the taste of foods made from the flour. (The cricket-size penacate beetle of the southwestern desert, a close relative of the flour beetle, has a similar defense. It stands on its head when disturbed and emits a foul-smelling cloud that can rival a skunk’s scent.)
Besides eating and spoiling food, flour beetles may also be carrirs of bacteria, molds and parasites. They are an intermediate host for the dwarf tapeworm, a parasite found in rats and mice that live off beetle-infested foods. Humans can become infected with the tapeworms by unwittingly eating infected beetles hiding in contaminated food.
Because flour beetles are masters of camouflage and concealment, it is not easy to detect an infestation in food. They are shy of light and will hide under food or in cracks and crevices when a room light is switched on. And, while other insects give themselves away by the droppings (pellets) they leave behind, flour beetles provide no such clue. Their excreta is often the same color as the food they’re eating. But nature did not create a perfect predator. The beetles do leave a telltale sign when they periodically shed their outer skins. These gold-colored skins stand out readily in the infested flour or other food.
A single beetle may shed its skin as many as 10 times. Such shedding is necessary for the four-stage growth from egg through larva to pupa and then adult. Shedding happens most often during the larva stage, when main growth occurs. The resting (pupa) stage–when the wormlike larva becomes an adult beetle–is the last time for shedding, or molt. One pair of adult beetles may live for two years and produce as many as 900 offspring, so it’s not surprising that a large number of skins (and pellets) accumulate in infested food in a relatively short time.
To detect and measure flour beetle contamination, FDA scientists have developed several methods for separating the insects from the food they contaminate.
An insect’s body shell will repel water but not petroleum solvents, such as kerosene. By mixing test samples of infested foods, water and solvent together, the beetles become saturated with solvent and the foods with water. Then the solvent floats to the top, bringing with it the beetles, to be skimmed off, identified and counted.
When whole beetles and parts aren’t detected in the examined samples, FDA scientists use a blue cloth filter and special washing techniques to find and count beetle eggs. If the grain–with beetles and all–has been ground into flour, the fragments can still be idenfitifed and counted, even though they are microscopic in size. FDA scientists have photographed and catalogued all body parts of the flour beetle larva and adult to help identify beetle fragments.
Out on inspection sites, such as food warehouses and grain elevators, FDA relies on the sharp eyes and experience of its field investigators to detect flour beetle infestations. The beetles manage to hide in all kinds of places, including corrugated cardboard packing, in the gear boxes of machinery where grain is ground into flour, and even in bait set out to control rodents. An FDA inspector with an eye for beetles can recognize unsanitary practices that permit beetle infestation and will see that the problems are corrected.
Flour, grain and other food products contaminated with beetles may not be sold for human consumption. Stored grain can sometimes be reconditioned by sifting and processing, but most often it and other contaminated foods must be converted to animal food or destroyed.
A good word for the thus-far pilloried flour beetle: For many scientists it is a valuable and useful insect. The structure of flour beetle genes is easily mapped and observed, which makes the bugs useful in genetic research. They are easy to raise in laboratory cultures and have a number of mutant genetic traits useful in cross-breeding experiments. But away from the laboratory–in the warehouses and granaries of the world–the flour beetle is seen as the dreadful little pest that it is.
COPYRIGHT 1986 U.S. Government Printing Office
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