There’s something so unsettling about opening a box of cereal or pasta, or scooping up a cup of flour or rice to find little bugs inside. These little pests are most likely weevils, a small black or reddish-brown insect with a snout.
Weevils are members of the Curculionoidea family, a type of beetle. There are around 97,000 species of weevils around the world. Many types of weevils destroy crops and stored grains in large bins, while others find their way inside your home, particularly your pantry, and make a home amongst your stored food.
If you’ve had the unpleasant surprise of finding these pantry pests in your food, welcome to the club. These pervasive pests are common all around the world. While weevils are a nuisance, they aren’t harmful to human health and are unlikely to carry infectious diseases.
Having weevils in your pantry is not a sign of uncleanliness—it’s likely from improperly stored food. (Don’t worry, we’re not judging!) And sometimes, weevils are already present in your food when you bring it home.
Read on to learn more about commonly found weevils.
Weevil size and shape
Weevils are small insects, typically around 0.25 inch (6 millimeters). They range in color from black to reddish-brown. Weevils are usually cylindrical or pear-shaped.
Since there are so many species of weevils and corresponding families, and subfamilies, there’s a wide range in shape and color. However, a distinguishing common characteristic is their pronounced snout and antennae, or ‘feelers.’ Some species have short and bent antennae, while others are long and straight.
Need help identifying pantry pests? Here are a few different websites you can check out:
Main types of pantry weevils
Let’s take a closer look at the main types of weevils you might find in your pantry. A few common foods you might find these unwanted visitors in include:
- Grains (oatmeal, cereals, etc.)
- Dried beans and seeds
- Dog food
Many people often refer to these insects as flour bugs or flour weevils, because they’re often found in flour bins, but they are actually one of the types of species listed below.
So what do weevils look like? Let’s take a closer look.
Perhaps the most common type of weevil you’ll have the displeasure of finding is the granary weevil (Sitophilus granarius) also known as the wheat weevil , grain weevil, or grain beetle. Granary weevils cause extensive damage to agricultural crops and are a farmer’s nightmare. They can also be pervasive pests when found in your pantry.
Granary weevils are around 0.08–0.12 inch (2–3 millimeters) long with a polished, reddish-brown color. They have an elongated snout that is about one-quarter the length of its entire body. Granary weevils, unlike its relatives the rice and maize weevils, cannot fly.
Adult females bite a hole in a single grain kernel where she lays an egg and seals it up. The egg then undergoes the larva and pupa stages until the young weevil bites its way out to emerge from the kernel. Females lay 50 to 200 white eggs during their lifespan. The eggs and larvae easily blend into grains making it nearly impossible to see.
The rice weevil (Sitophilus oryza) has the ability to fly allowing it to travel and spread more easily. It’s around 0.11–0.18 inch (3–4.6 millimetres) long. They have a dull reddish-brown to black color with four spots on its back that can be red or yellow. As the name suggests, rice weevils feed on rice grains.
Similar to the granary weevil, rice weevil eggs are also deposited inside a kernel of grain to emerge later as an adult. Females lay 300 to 400 eggs during their lifespan. Hot weather can speed up the development of eggs while cool weather can prolong it. On average it takes 26 days from egg to pupa stage.
Just like the rice weevil, the maize weevil (Sitophilus zeamais ) has fully developed wings enabling it to fly. You might find the maize weevil in your box of pasta, or cereal.
It ranges in size from 0.09–0.19 inch (2.3–4.9 millimeters). With a smaller snout than the granary weevil, it has a dull reddish-brown to black color. The thorax is pitted with a smooth thin strip running down its dorsal. While very similar to the rice weevil, the maize weevil is often slightly larger.
Like its other relatives, the maize weezil also chews a hole through a kernel of grain to lay an egg. The maize weevil has a slightly longer development period than the rice weevil taking at least 30 days to go from egg to pupa.
While called a “weevil” the bean weevil (Acanthoscelides obtectus) is actually classified under the beetle family Chrysomelidae. As such it doesn’t have the long snouts characteristic of other “true weevils.” It also has a tucked-under head. You might find these insects inside your pantry feasting on dried beans or seeds.
Ranging in size from 0.04–0.87 inch (1–22 millimetres), bean weevils are either dark brown or black with a distinct mottled pattern. The females lay eggs onto seeds. As the larvae develop, they bite into a seed and make sure to leave an exit for later.
An interesting trait of adult bean weevils is that they curl up and play dead when they’re disturbed.
How did weevils get in my pantry?
Some types of weevils make their way into your home through cracks in walls, doors, and windows when the weather gets too hot or dry outside. Others come home with you undetected as eggs, larvae or pupae hidden inside kernels of rice, grains or seeds.
Granary weevils in particular have become especially well adapted to making their homes inside large storage containers where they are packaged and shipped to grocery stores and brought home by unwitting hosts.
Want to swear off eating all forms of grains and seeds forever? While it’s disgusting to think that we’re unlikely eating weevil eggs, or larvae, it’s important to remember that most food products likely carry some insects. After all, it’s almost impossible to filter out all insects during harvesting, processing, packaging, and shipping.
Don’t worry, weevils don’t bite
While they’re definitely a nuisance, weevils don’t bite or sting humans, or household pets. They prefer to bite into your stored pantry goods, thank you very much.
Using heat or cold to kill weevils
If you’ve removed the adult weevils in your pantry and are still concerned with any eggs or larvae left behind, don’t bother trying to search in, say, a bucket of rice. They are so small and camouflaged so well. A better method would be to use heat or cold to kill the larvae.
Try freezing food for a minimum of four to seven days. Or, try placing grains in an oven at 140 degrees Fahrenheit for 15 to 20 minutes.
And if you’re still not feeling better, you can just throw the food out.