There are two different types of beetles classified as flour beetles: the red flour beetle and the confused flour beetle. Both are similar in physical characteristics. They are flat and oval in shape and usually range around 1/8- inch long. Their exoskeleton is reddish brown with a shiny and smooth texture. The eggs, larvae, and pupa resemble each other closely in physical features as well. The eggs usually tend to be a white color, or at times even colorless. They are very small in size and have a sticky outer covering that causes certain food particles to stick to it. The larvae have six legs, with two pointy projections toward the caudal end. Finally, the pupal stage (a cocoon-like form used to break itself down and emerge as a mature adult) is usually a white or brownish color. The beetle life cycle lasts approximately 3 years or more, with the larval stage ranging anywhere from 20 to over 100 days, and the pupal stage around 8 days. Beetles usually breed in damaged grain, grain dust, high-moisture wheat kernels and flour. The female flour beetle can lay between 300 and 400 eggs during her lifetime [a period of 5 to 8 months]. The flour beetles mainly infest grains, including, but not limited to: cereal, corn meal oats, rice, flour, and crackers. This type of beetle is the most abundant insect pest of flour mills across the United States. Their small size allows them to maneuver through cracks and crevices and get into the home and other areas. Once they are present in areas with potential food sources, they can infest material such as flour, resulting in a sharp odor or moldy flavor. The red flour beetle is able to fly short distances and the confused flour beetle is unable to fly. While the confused flour beetle is more commonly found in the northern United States, the red flour beetles are more predominant in the southern United States in areas with warmer climates. The red flour beetle is considered the best organism to study genetics. A team composed of Susan Brown and Rob Denell, both biology professors at the University of Kansas, along with Richard Beeman, won financial support to have the beetle's genome sequenced, marking it as one of the earliest sequenced insect genomes, as well as distinguishing the red flour beetle as the only pest insect to be analyzed in this way thus far. The project was funded partially by the US Department of Agriculture, as well as by the National Institutes of Health, and the genome sequencing was led by Stephen Richards at the Human Genome Sequencing Center, Baylor College of Medicine. The red flour beetle's gene map information and genomic sequence are accessible from the National Center for Biotechnical Information. More information is to be published in Nature on 2008-03-27.
The biscuit beetle is closely related to the commonly known cigarette beetle. Adult drugstore beetles are shaped cylindrically with dimensions ranging from 2.25 to 3.5 mm. Their exoskeleton consists of a reddish brown coloring. These beetles are also characterized by elytra, sclerotized (hardened) wings that fold back over the abdomen and hinge upwards, allowing the hind wings to come out in order to fly. The presence of this striated appearance helps distinguish the drugstore beetle from a similar species, the cigarette beetle. Females are capable of laying up to 75 eggs during a life time. After the eggs are laid they move into a larval period that can range anywhere from 4 to 20 weeks. After the larval period, drugstore beetle larvae move out of the substrate to build a cocoon and pupate. The pupation process takes a total of 12-18 days. The entire life cycle of the drugstore beetle lasts approximately 2 months but can be as long as 7 months. Adult female beetles have a lifespan of about 13 to 65 days. These stored product pests will infest almost anything readily available. Food products prone to infestation include: flours, dry mixes, breads, cookies and other spices. Non-food material includes: wool, hair, leather and museum specimens. This specific type of beetle is able to produce symbiotic yeasts that produce B vitamins, which allow the beetle to survive on the consumption of poor nutritional foods. They are found in areas that have a warmer climate, yet are less plentiful among the tropics as their counterpart, the Cigarette beetle.
The sawtoothed grain beetle is closely related to the merchant grain beetle, and is commonly found in kitchen cabinets feeding on items such as cereal, breakfast foods, dried fruits, macaroni, crackers, etc. They are the most common grain and stored product pest. They are very active and tend to crawl rapidly while searching for food. They are small insects, reaching roughly around 1/8 of an inch. Their name originates from their distinguishable saw-tooth-like projections found on each side of the thorax. The body shape of the beetle is flat, slender, and brown in color. The size and shape of the mandibles allow the beetles to easily break through well sealed and packaged foods. An adult female sawtoothed grain beetle can lay anywhere between 45 to 250 eggs, that usually hatch within 3 to 17 days. The larvae look much different from the mature adult. They have a caterpillar-like appearance, with a yellowish coloration to the body and a brown head. The larval period can last as long as 10 weeks but can be as short as 2 weeks. Following the larval instars is the pupal period, which can last one to three weeks. The pupal stage is characterized by the unique process by which these beetles stick together pieces of food material to form a protective covering around their bodies. A fully mature adult beetle, under optimal conditions, can live a maximum of 4 years, a considerably long arthropod lifespan.
Indianmeal moths can infest a variety of foods found in the pantry. Coarsely ground grains, cereals, dried fruits, and herbs are common items the moths have been known to infest. They have also been found in animal food such adried dog food, dried fish food, and even bird seed. The adult moth is small; generally, their size averages about 3/8 inch, with a 5/8 inch wing span. As adults, the moths are easily identified by an overall grayish, dirty complexion. However, the wing tips have a bronze color that helps differentiate this particular moth from other household moths. The adults have a distinct forewing pattern as well. The pattern consists of a light-colored base with about two-thirds of the distal area a red to copper color. The larval stage, or caterpillar, is characterized by a pinkish or yellowish-green body color with a dark brown head. The larval stage of the moth’s life cycle is centered on food sources; during the last instar, these larvae are characterized by a movement towards a protected area to pupate. These caterpillars have the capacity to chew through plastic packaging and will often produce silk that loosely binds to food fragments. The pupal stage is generally observed as tiny cocoons that hang from the ceiling; these cocoons can also be found on walls, as well as near the food source. A female can lie over 200 eggs, and will usually die after this process because adults Indian meal moths do not eat.
Fruit flies are found near ripened or fermenting fruit. Tomatoes, melons, squash, grapes and other perishable items brought in from the garden are a common cause of an indoor infestation. Fruit flies can also be attracted to rotting bananas, potatoes, onions and other unrefrigerated produce purchased at the grocery store and taken home. The body of the fruit fly is tan towards the front part of the body and black towards the rear. They usually have red eyes and are about 1/8 inch long. Females have the ability to lay over 500 eggs, usually in fermenting fruit as a food source. The only environment necessary for successful reproduction is a moist film and fermenting material. Generally, fruit flies are a problem during late summer and fall due to their attraction to ripening and fermenting fruits and vegetables. The entire life cycle can be completed in about a week. Unfortunately, because of their ability to fly in and out of the home through windows and screens, they have the capability of contaminating food with bacteria and disease-producing organisms.
Careful observation is necessary when detecting the culprit of an insect infestation. Each of the five different insects discussed has a unique pattern of destruction. These observations are imperative, as there are not always larvae, pupa, or adults readily available for examination and identification. In the absence of physical specimens, conclusions can be drawn about the probable insect that is infesting the product just by noting the damage done to the particular food. By noting the type of food and the damage done, a nearly accurate conclusion can be drawn about the type of insect causing the damage, allowing a conjecture about the type of control needed. Having an insect specimen and accurately identifying it can lead to eradication, and ultimately, prevention. Foods commonly infested include:
Other items include, but aren’t limited to: Rodent baits (that contain grain as a feeding attractant), dry pet food, bird seed, grass seed, some powdered soap detergents, dried flowers, potpourri, items stuffed with dried beans or other plant material, and tobacco products.
In order to identify an insect, and consequently make a decision about the type of control to be implemented, the type of food must first be noted, especially in the absence of a specimen. Although identifying the food is a general start to begin to identify the insect, it must be remembered that it isn’t always the most accurate method. It is mostly used as a guideline, as some insects are more likely than others to be found in certain types of grain, flour, etc. The type of food is not always conclusive to the type of insect found in it, as insects are not extremely picky, and many families and species are found on a wide range of different foodstuffs. Using the infested item as a guideline, noting the type of damage done to the product is the next step. Some insects, like the drugstore beetle, leave telltale tiny holes in the damaged product, while Indianmeal moths are notorious for the spider web-like threads left behind in the food they infest. These observations can generally lead to a mostly accurate conclusion about the type of insects that are causing the damage, but obviously the most accurate conclusion relies on any specimen found either directly in the stored product or in the vicinity. The larvae, pupae, and adults can be found directly in the product while usually only the pupae and adults are found in the vicinity of the product. It is not practical to assume that any person has knowledge of general entomology, so the following analysis focuses on the five major pests that most commonly infest stored products, beginning with the type of foods infested, signs indicative of a particular insect infestation, and a description of the larvae, pupae, and adults, including behavior as well as appearance.
The sawtoothed grain beetle feeds on a plethora of feeds, but is not capable of attacking whole or undamaged grains; therefore, it is commonly found in processed grains (flour and meal), dry dog food, dried fruits, candy bars, tobacco, drugs, dried meats, and a variety of other products. It is one of the most common insects found to infest stored products. Larvae are found to develop in flour, dried foods, cereal products, and other stored products.
These beetles will infest almost anything- they are found most often, however, in flour, bread, spices, breakfast foods, and meal. In the case of an infestation, contaminated products have telltale tunnels which have the appearance of tiny holes. These beetles do not sting, bite, or harm pets or damage a house, yet have the potential, in large infestations, to become a nuisance by flying on doors and windows in heavy populations.
Larvae are white worms with black heads, which, when ready to pupate, crawl up the walls of the home in most cases, and are suspended from the ceiling attached by a single silken thread. Most complaints about these moths come during the warmer parts of the year- usually the months of July through August- but the moths have the capability to appear during any month. As with all insects important to stored product entomology, it cannot be automatically assumed that products were previously infested, yet, it is more common for these moths to hitchhike inside a product or in groceries than for the moth to fly into a home through open windows or doors. An important aspect of the Indianmeal moth is that the larvae are the only stage of the insect’s life cycle to feed on stored products, the adults do not.
Fruit flies are attracted to ripened fruits and vegetables, usually in the kitchen area, but will breed in garbage disposals, empty bottles and cans, wet or damp mops or cleaning rags, and trash containers. The only requirement for these flies to breed is a moist film of fermenting material. Infestations can originate from over-ripened fruits or vegetables that were previously infested, and then brought into the home or from fruit over-ripening in the home. Since adults can also fly from the outside through screened doors or windows it can not always be assumed that the product in question was infested before it was brought into the home. The larvae are found on the inside layer of the fruit, just directly beneath the skin. If the outer layer of the fruit is removed, the rest of the fruit can be salvaged. Fruit flies are primarily a nuisance pest, yet they can infect food with bacteria and other organisms that cause diseases.
Major companies spend a large amount of money every year to aid in the prevention of food contamination. Most of these dollars are well-spent and do, in fact, prevent food from becoming contaminated on a large scale; however, there are many "defects" in consumers' meals on a daily basis. The Food and Drug Administration states, “it is economically impractical to grow, harvest, or process raw products that are totally free of non-hazardous, naturally occurring unavoidable defects”.
The general public proposes that companies should use more chemicals or pesticides to control this “problem”. Though, the amount of pesticide and chemicals necessary to eradicate all insects from foodstuff would pose a threat to any human’s health; much more harmful than a controlled quantity of insect and rodent fragments. The Food Defect Action Levels, as proposed by the FDA, is a list of ordinances and guidelines manufacturers and industrial food agencies must abide to ensure the safe service of foodstuff. However, these detection levels are labeled with maximum limitations only. Due to the impossibility of preventing all unavoidable defects in foods, the FDA attempts to prevent these health hazards from reaching a harmful level. Therefore, it is understood and regarded that all manufactures are allowed to have low numbers of insect and rodent hairs present in food, as long as the product is still considered “safe” for human consumption. Shown below are a few examples taken from the FDA's Defect Action Level Handbook:
DEFECT SOURCE: Mold - post harvest infection. Rodent hair -
post harvest and/or processing contamination with animal hair. Whole
or equivalent insects - preharvest, and/or post harvest and/or
processing insect infestation,
SIGNIFICANCE: Aesthetic
| CHOCOLATE AND CHOCOLATE LIQUOR | Insect filth (AOAC 965.38) |
Average is 60 or more insect fragments per 100 grams when 6
100-gram subsamples are examined OR Any 1 subsample contains 90 or more insect fragments |
| Rodent filth (AOAC 965.38) |
Average is 1 or more rodent hairs per 100 grams in 6 100-gram
subsamples examined OR Any 1 subsample contains 3 or more rodent hairs |
|
| Shell (AOAC 968.10-970.23) |
For chocolate liquor, if the shell is in excess of 2% calculated on the basis of alkali-free nibs |
| CITRUS FRUIT JUICES, CANNED | Mold (AOAC 970.75) |
Average mold count is 10% or more |
| Insects and insect eggs (AOAC 970.72) |
5 or more Drosophila and other fly eggs per 250 ml or 1 or more maggots per 250 ml |
| CORNMEAL | Insects (AOAC 981.19) |
Average of 1 or more whole insects (or equivalent) per 50 grams |
| Insect filth (AOAC 981.19) |
Average of 25 or more insect fragments per 25 grams | |
| Rodent filth (AOAC 981.19) |
Average of 1 or more rodent hairs per 25 grams
OR Average of 1 or more rodent excreta fragment per 50 grams |
| HOPS | Insects (AOAC 967.23) |
Average of more than 2,500 aphids per 10 grams |
| PEANUT BUTTER | Insect filth (AOAC 968.35) |
Average of 30 or more insect fragments per 100 grams |
| Rodent filth (AOAC 968.35) |
Average of 1 or more rodent hairs per 100 grams | |
| Grit (AOAC 968.35) |
Gritty taste and water insoluble inorganic residue is more than 25 mg per 100 grams |
| PEPPER, GROUND | Insect filth (AOAC 972.40) |
Average of 475 or more insect fragments per 50 grams |
| Rodent filth (AOAC 972.40) |
Average of 2 or more rodent hairs per 50 grams |
| WHEAT | Insect damage (MPM-V15) |
Average of 32 or more insect-damaged kernels per 100 grams |
| Rodent filth
(MPM-V15) |
Average of 9 mg or more rodent excreta pellets and/or pellet fragments per kilogram |
| WHEAT FLOUR | Insect filth (AOAC 972.32) |
Average of 75 or more insect fragments per 50 grams |
| Rodent filth (AOAC 972.32) |
Average of 1 or more rodent hairs per 50 grams |