An approximate 3 – 4mm in length, adult confused flour beetles are a red-brown in colour and typically distinguished by antennas which broaden gradually at the tip. These insects possess the ability to fly but rarely do so. Their larvae are whitish to yellow-brown in colour, 1 – 5mm long in size.

Covered in golden-yellow hairs, the Golden spider beetle has an ovoid abdomen with a pinched waist and adults grow to approximately 2 – 4.5mm in length.

Both of these flour beetles are considered a stored product pest that can be found in residential and commercial settings. They can cause considerable financial losses in food processing centers, food mills and commercial storage areas. The red flour beetle, confused flour beetle, sawtooth grain beetle, and Indian Meal Moth are the most predominant stored product pests in homes and gocery stores.

Confused flour beetles have a preference for clean flour, feeding on and pupating in flour and cereal products.

Larder beetles have a lifespan of approximately 2 – 3 months at 18 - 25°C.

There are two types of Flour Beetles – the Confused Flour Beetle and the Red Flour Beetle. Both of these Flour Beetles have unique physical characteristics and qualities. They are also found in different areas.

Figure 8. Larva of a flour beetle, Tribolium sp. Photograph by Rebecca Baldwin, University of Florida.

Controlling flour beetles starts with a thorough inspection. Every infested package should be thrown away. Vacuum the pantry and cabinet shelves. This will remove food particles. Store new food products in sealed containers to prevent new infestations.

Figure 5. The front (left), middle (middle) and hind (right) legs of the red flour beetle, Tribolium castaneum (Herbst), showing the 5-5-4 tarsal formula. The confused flour beetle, Tribolium confusum Jacquelin du Val, has the same tarsel formula. Photographs by Rebecca Baldwin, University of Florida.

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Tropical warehouse moths have a lifespan of 31 days at an optimum temperature of 32°C.

Sighting of small tubular beetles near stored products or in the product can indicate activity.

The larvae hatch and begin to eat the material where they hatched. The larvae are 4 to 5 mm long. Flour beetles can develop from egg to adult in as little as seven weeks. In warm environments, there can be four or five generations per year.

Figure 10. Life cycle of a flour beetle, Tribolium sp. Photograph by Rebecca Baldwin and Andrew Koehler, University of Florida.

In red flour beetles, males are known to engage in polygamous behavior. Research largely shows that Male red flour beetles engage in polygamous behavior to avoid inbreeding depression, especially when there is competition from other males. There is a higher fertilization success in out-bred males when they compete with inbred males to fertilize the same female.[12]

The biscuit beetle has a humped thorax and a body covered in fine hairs, their wing cases have ridges with indentations. Adults grow to an approximate 2 – 3mm in length and larvae are known to be active in early stages of development.

With round indentations on the thorax and reddish spots on their wing cases, the rice weevil can grow up to an approximate 2 – 3mm in length.

Characterised by 6 saw-like projections on each side of the thorax, the saw toothed grain beetle has a long length of head behind the eyes. Adults grow to approximately 2.5 – 3mm in length and their larvae a yellow to brown in colour, with a brown head.

This species closely resembles the confused flour beetle, except with three clubs at the end of each of its antennae.

Surviving approximately 98 days at 18°C, rice weevils can live for several months to a year in favourable conditions. Larvae will not develop below 16°C.

Highly resistant to cold temperatures, females lay about 275 – 600 white, bean-shaped eggs singly or in clusters during spring, which hatch into larvae in 4 – 14 days. The pupal stage lasts 7 – 24 days – first white, turning yellow (not enclosed in a cocoon) and finally emerging as adults with a lifespan of 2 – 3 months.

If you’re uncertain if you have an SPI problem or not, you can find all the signs to look out for here.

Red Flour Beetles larvae and pupae.(Actual Size - 1/8 inch). The Red Flour beetles goes through a complete metamorphosis - egg, larvae, pupae, and adult.

The pupae are lighter in color, being white to yellowish.

Although small beetles, about 1/8 of an inch long, the adults are long-lived and may live for more than three years (Walter).

The red rust flour beetle has close set eyes, and the last three segments of their antennae form a club. Adults grow up to approximately 3 – 4mm in length and fly in warm climates.

The size of booklice varies according to species, typically 1 -2 mm long, they range from a pale yellow-brown to dark brown in colour. Nymphs are very small and often appear transparent.

Surviving for 35 days at 35°C, the Indian meal moth lives for much longer at lower temperatures or when feeding on low nutrition foods.

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Possessing the ability to fly, the cigarette beetle feeds on a wide range of stored products including tobacco, cereal, pulses, dried fruit and spices.

Surviving approximately 20 days at 35°C and 3 – 4 months at 20°C, the saw tooth grained beetle is comparatively more tolerant to temperature extremes than other pest beetles.

Red Flour Beetle

The cheese mite favours warm, moist conditions and eggs mature in 10 days at room temperatures. Females can lay up to 900 eggs in a lifetime at a rate of 20 – 30 a day. Adult cheese mites can live for up to 60 – 70 days.

Approximately 20mm long, yellow mealworm beetles are shiny, dark-brown or black. Larvae are a honey-yellow color with hard, highly polished worm-like body.

Adult beetles of these two flour beetles have shiny, reddish brown bodies that are about 1/7 inch long, flattened, and oval.

Covered in brown and golden hairs, the Australian spider beetle has a spider-life appearance and adults grow to an approximate 2.4 – 4mm in length.

Flour beetles do not attack whole grains. The female beetle deposits eggs directly on flour, cereal, dry pet food or other similar products. The females deposit a few eggs each day in the food that she is eating. The egg laying can last several months. The eggs are hard to see in flour or meal.

Penn State College of Agricultural Sciences research, extension, and resident education programs are funded in part by Pennsylvania counties, the Commonwealth of Pennsylvania, and the U.S. Department of Agriculture.

Learn the feeding habits and lifecycles of stored product insects and the damage they can do if left uncontrolled.

The red flour beetle is reddish-brown in color and its antennae end in a three-segmented club (Bousquet 1990). Whereas the confused flour beetle is the same color but its antennae end is gradually club-like, the "club" consisting of four segments (Walter).

Surviving approximately 30 days at 30°C, grain weevils can live for up to 8 – 16 weeks in favourable conditions.