Do Grain Beetles Fly? Uncovering the Truth About These Pests

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Grain beetles are common pests in stored grains and can pose a significant problem for agriculture. There are a few different species of grain beetles, including sawtoothed grain beetles and merchant grain beetles, which have slightly different life cycles and behaviors. Knowing whether these beetles can fly is important for understanding their potential to spread and infest grain storage facilities.

The foreign grain beetle is a small reddish-brown insect, often mistaken for fruit flies or gnats due to their strong flying ability. On the other hand, sawtoothed and merchant grain beetles, despite having wings, are not known for their flying prowess.

Do Grain Beetles Fly

Sawtoothed Grain Beetle vs Merchant Grain Beetle

Grain beetles are common pests found in stored products, specifically infesting broken grain and processed grain products. Among the grain beetles, there are two primary species: the sawtoothed grain beetle and the merchant grain beetle.

Sawtoothed Grain Beetle

  • Scientific name: Oryzaephilus surinamensis
  • Appearance: Saw-like projections on the pronotum
  • Flight: Does not fly
  • Attraction to light: Not attracted to light

The sawtoothed grain beetle is not capable of flight, and they are not attracted to light. These beetles are named after the saw-like projections found on their pronotum.

Merchant Grain Beetle

  • Scientific name: Oryzaephilus mercator
  • Appearance: Similar to sawtoothed grain beetle, without saw-like projections
  • Flight: Capable of flight
  • Attraction to light: Attracted to light

On the other hand, the merchant grain beetle is indeed capable of flight, and they prefer light. These beetles are closely related to the sawtoothed grain beetle but lack the characteristic saw-like projections.

Comparison Table

Sawtoothed Grain Beetle Merchant Grain Beetle
Flight capability No Yes
Attraction to light No Yes

In summary, sawtoothed grain beetles do not fly and are not attracted to light, while merchant grain beetles can fly and are attracted to light.

Grain Beetle Identification

Physical Characteristics

Grain beetles are small with a flattened body shape, typically measuring between 1/10 and 1/8 inch in length. They are brown or reddish-brown in color. Their flat bodies make it easy for them to crawl into tiny crevices. Some grain beetles have distinct features, such as saw-like projections or peg-like structures behind their head. To identify grain beetles, entomologists often use a magnifying glass to examine these features more closely.

Common Types of Grain Beetles

There are two common types of grain beetles that are often encountered in households: sawtoothed grain beetles (Oryzaephilus surinamensis) and merchant grain beetles (Oryzaephilus mercator).

  • Sawtoothed grain beetles have six saw-like teeth on the first segment behind the head.
  • Merchant grain beetles have two peg-like projections behind their head.

These two grain beetles have similar sizes, colors, and body shapes, which can make it challenging to distinguish them without using a magnifying glass to examine the mentioned unique features. Below is a comparison table illustrating key differences:

Sawtoothed Grain Beetle Merchant Grain Beetle
Unique Feature 6 saw-like teeth 2 peg-like projections
Scientific Name Oryzaephilus surinamensis Oryzaephilus mercator
Flight Capability No* Yes

(*) Some sources mention that sawtoothed grain beetles do not fly, while others mention that merchant grain beetle can fly. However, this information may vary between sources and individual specimens.

When dealing with a grain beetle infestation, it is essential to correctly identify the beetle type to decide on the most effective control method. In case of doubt, consult an entomologist or pest control professional for assistance.

Life Cycle and Habits

From Egg to Adult

Grain beetles go through a complete metamorphosis during their life cycle, which includes egg, larvae, pupa, and adult stages.

  • First form: egg
  • Second form: larvae
  • Third form: pupa
  • Fourth form: adult

The length of the life cycle can vary among different species of grain beetles. Some may take 2-5 years to complete their life cycle, while others may have several generations within a year1. In general, a beetle stays in the egg stage for about 7-10 days before they hatch into larvae2.

Larvae stage is where grain beetles undergo rapid growth. Like mealworms, the larvae of some species are used as a food source for animals3.

Next comes the pupa stage, during which beetles transform into their adult form. The duration of pupal stage varies depending on the species and environmental factors.

Once they reach the adult stage, grain beetles are capable of flying4. They are attracted to grains and other stored food products, making them a nuisance in households and commercial premises.

Table 1: Comparison of Grain Beetle life stages

Life Stage Duration Characteristics
Egg 7-10 days Small, difficult to see
Larvae Varies Rapid growth, used as food for animals
Pupa Varies Transformation into adult form
Adult Varies Capable of flying, attracted to grains

Causes of Infestation

Pantry Pests

Grain beetles are a common type of pantry pest that can infest a variety of stored food products. They are attracted to cereals, nuts, pasta, dried fruits, chocolate, bread, and sugar. These pests can infest food containers that are replenished without being emptied and cleaned first.

Two types of grain beetles include:

  • Foreign grain beetles: Small, flattened, reddish-brown insects, about 1/12 inch long. They can be identified by two peg-like projections behind their heads 1.
  • Sawtoothed and merchant grain beetles:

Damage and Harmful Effects

Impact on Grains

Grain beetles are a significant problem for stored grain products. These insects have hard shells and can fly, making them difficult to handle and control 1. Some examples of products they infest include:

  • Grains
  • Flour
  • Pet food
  • Drugs
  • Tobacco

Grain beetles can cause significant damage to these products by:

  • Contaminating them with their excrement
  • Feeding on and reducing the weight of the grains
  • Introducing mold and fungi

Stored Products

When grain beetles infest stored products, they can result in economic losses for businesses and households. They are known to cause the following issues:

  • Reduction in quality of stored products
  • Shortened shelf life due to contamination
  • Increased costs for pest control and product replacement

Comparison Table:

Grain Beetles Other Pests
Mobility Can fly Varies
Products Grains, Flour, Pet food, Drugs, Tobacco Depends on pest
Damage Contamination, product weight reduction, mold introduction Varies
Economic Impact Product loss, increased pest control costs, lower business reputation Depends on pest

By better understanding the damage and harmful effects of grain beetles, individuals and businesses can take appropriate measures to manage and prevent infestations.

Prevention and Control

Sanitation and Food Storage

  • Make sure to inspect your pantry regularly for any signs of grain beetles.
  • Clean your shelves and pantry regularly to prevent grain beetles from hiding and breeding.
  • Store food items in tightly sealed plastic containers to avoid infestations.
  • Dispose of infested food items immediately.

An example of proper food storage methods:

Food Storage Method Advantages Disadvantages
Plastic Containers Airtight, Durable Cost, Space
Glass Containers Airtight, Durable Cost, Breakable
Paper Bags Low cost, Biodegradable Not Airtight, Easily Damaged

Pest Management Practices

  • Keep an eye out for grain beetles in small cracks and crevices around your home.
  • Use a vacuum to clean up any beetles you find while cleaning or inspecting your home.
  • Consult professional exterminators if the infestation gets out of hand.

As humans, we play a big role in pest prevention and management. Proper sanitation practices, food storage methods, and professional pest management assistance are crucial for keeping grain beetles under control. It’s essential to take these steps to maintain a clean and beetle-free environment.

Treatments and Solutions

Insecticides

Insecticides are an effective way to control grain beetle infestations. Two common insecticides used for this purpose include:

  • Pyrethrin: A natural insecticide derived from chrysanthemum flowers. It is effective against many stored product pests like grain beetles and weevils.
  • Malathion: A synthetic insecticide used to control various insects, including saw-toothed grain beetles and weevils.

Pros:

  • Effective in controlling infestations.
  • Wide range of products available for different pests.

Cons:

  • May require multiple applications.
  • Some insects may develop resistance over time.
Insecticide Derived from Effective Against
Pyrethrin Chrysanthemum flowers Grain beetles, weevils
Malathion Synthetic compound Saw-toothed grain beetles, weevils

Aerosols

Aerosols, such as Novacide, can also help address grain beetle infestations. They are typically applied in areas where the beetles are active, such as stored grain or product storage spaces.

Pros:

  • Easy to apply.
  • Can quickly kill exposed beetles.

Cons:

  • Less effective for deep infestations.
  • May require reapplication over time.

When dealing with grain beetle infestations, it’s also essential to:

  • Practice good sanitation by vacuuming and cleaning areas where grain is stored.
  • Monitor for pests regularly.
  • Ensure proper storage and handling of grains to reduce the risk of reinfestation.

Further Resources and Assistance

If you’re looking for resources on grain beetles, UMN Extension offers information on identifying and managing foreign grain beetles. These beetles are small, flattened, reddish-brown insects with peg-like projections behind their heads. They can be mistaken for fruit flies or gnats.

To differentiate between grain beetles and other insects, note that beetles have a hard shell, unlike flies. Additionally, [UMaine Cooperative Extension](https://extension.umaine.edu/ipm/ipddl/publications/5034

Footnotes

  1. Wisconsin Horticulture 2 3

  2. Ask A Biologist

  3. Beetle Reproduction | Ask A Biologist

  4. Foreign grain beetle | UMN Extension

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Pantry

 

How To Get Rid Of Pantry BeetleHELP! What Are These Bugs?!
Dear Bugman,
HELP! These bugs are driving me crazy trying to figure out what they are and how to get rid of them! They seem to be more of a nuisance to me more than anything because I do not know what they are and I cannot find any info on them to be able to know what they are. I keep finding them on our hardwood floor, mainly along the baseboards, in the hallway between our baby’s room and our room (which are right across from each other). We live in Columbia, SC.
The first time I ever saw one of these bugs was in my baby’s baby cereal box, which I then threw out the whole box after seeing that. After that I started storing her baby cereals in sealed tupperware containers. Then, not too long after that I found a couple of them on the kitchen counter. But, I haven’t seen any of them anywhere in the kitchen since then.
Ok, now I cannot find any in the kitchen at all. I’ve looked through our cabinets and cereals, (we do not have any flour), and I’ve also looked all through our pantry and cannot find any there either. The only place I’m finding them now is in the hallway where I told you, between the two rooms, closer to the baseboards. And I have found a couple on the bathroom floor also. There are a few on the floor in the linen closet, also closer to the baseboards, which is between the two bedrooms in the hallway where I keep finding them.
What really confused my husband and I about these bugs was that one time when we were going through things in our attic, we got out some older VHS video tapes and a few of these bugs had fallen out of the VHS tapes. Then my husband continued to keep knocking the video tapes on the floor and they just kept falling out of the tapes. They were all dead though. Finally, after so many of them, they stopped falling out.
Then when we brought down the box with our Christmas decorations in it, to our surprise, there were all these same little bugs (a whole bunch of them) stuck to, and stuck underneath, the masking tape on the outside of the box. Yuck!!! I kept thinking "Why are these things so attracted to the masking tape like this?!" I’ve attached a few pics of these little creatures that are on my last nerve, one of the pics being of them stuck on the masking tape. So, obviously they’re in the attic also.
Our neighbors have them in their cupboards every now and then. They call them Weevils, but I don’t think that’s what they are. I’ve been looking all over the internet trying to figure out what these things are and I cannot find anything that looks like these bugs. They are like tiny little brownish beetle looking bugs.
I don’t see how they can be Pantry Beetles, because I haven’t been able to find any in the kitchen anywhere. They are driving me crazy, because everytime I pick up the ones that I keep finding on the floor in the hallway between the bedrooms, a few hours later a couple more have showed up around the same spots. And you know, they don’t move unless I nudge them a little.
WHERE ARE THEY COMING FROM?!
WHAT ARE THEY?! AND HOW DO WE GET RID OF THEM?!
PLEASE HELP BUGMAN!
Thank you,
Seriously Curious

Dear Seriously Curious,
You do have Pantry Beetles, but there are many species, some of which are weevils. You might have the Merchant Grain Beetle, Oryzaephilus mercator, or a member of the genus Cathartus. These beetles are especially a problem in the humid South. These are small elongate reddish beetles that feed on grain and dried fruits in the larval stage, but when they mature, they fly away to a new food source, often pollen. You might have large numbers of adults congregating where they think they can get access to the outdoors, hence the attic. Aslo sticky tape will trap them like fly paper. The larvae will also eat dried pet food or even a forgotten box of cookies in some seldom used closet. Could someone in the house be hiding (hoarding) food and have forgotten it? If they are really that plentiful, you might want to fumigate, though we believe that could do more harm than good.

Letter 2 – Pantry

 

What this bug?
Dear Bugman,
First, congrats on a great site!
Attached are two closeups of a bug, possibly a bed bug, found when stripping the sheets from our mattress. (We do this every week, but this is the only ‘visitor’ we’ve ever seen). Bug was not dead, but just lying there waving its little legs slowly. Could be because we had had a flea infestation (we>lying there waving its little legs slowly. Could be because we had had a flea infestation (we>sprayed the house and mattress with flea spray last year. Any way here it is…

Dear Richard,
I really wasn’t positive, so I sought out a true expert, Weiping at the Museum of Natural History in Los Angeles. Here is his answer:
“Thank you very much for your image. This is a Thylodrias larva (Coleoptera: Dermestidae: Thylodrias). It is very common in Los Angeles area. I collected it many times in our museum. Hopefully, the information will help you. Sincerely, Weiping”
I can add the Dermestidae is a family of beetles known as Carpet Beetles or Buffalo Bugs. They are fond of eating skins, furs, woolen materials and dried animal matter, and as a family, are the bane of the entomologist since they can quickly devour a prized insect collection.

Many thanks for the reply – I’m greatly relieved that its only a carpet beetle, and not something worse! Attached the second picture, which was of the head/jaws of the grub.
Best Regards, Richard

Dear Richard,
Thank you for the additional photo. I did find some additional information for you. The beetle Thylodrias contractus does not have the typical form of most Carpet Beetles. It is more elongate with long legs and antennae. I did find an interesting anecdote in Lutz’ book Field Book of Insects. He writes: “In 1908 Mrs. Slosson, the author of such charming stories as ‘Fishing Jimmy,’ published a description of a strange beetle that was eating her collection of insects. She playfully called it ‘Ignotus aenigmaticus.’ This name was in proper form and by the rules of the game remained the scientific name of the beetle until the discovery was made that the beetle was an introduction from Transcaucasia and had a prior name. It is now Thylodrias contractus. It eats like a Dermestid but does not look like one. The female is wingless and the male has no hind wings.” The beetle was originally described in Transcaucasia by Motschulsky.

Thanks again Daniel – two further questions,
1. do you have a picture of an adult?
2. Will my bug make it onto your website?

Hi Richard,
I have your letter ready for posting, but the site is currently down due to heavy traffic. I was expecting it to be up today, but still no luck. I know the site is up on the east coast, since I began getting additional letters. Check in a day or two. I have a photo of an adult and will attach it. It was previously identified only generally, but now there is an exact species name. Thank you for your interest.
Daniel

Letter 3 – Pantry

 

Hello, we live in Tampa, Florida and we have recently been seeing these beetles in our home. They are brownish in color, about 1/16 of an inch in length, are more active at night, can fly and seem to be attracted to light. They also appear to like linens and laundry. I am trying to find their access to the home as they disturb my daughter at night.
Thank you,
Adam Matthews and Family

Dear Adams Family,
Most of the time when small beetles appear in the home, they are some type of pantry beetle. The larvae feed on a wide variety of grain products in the pantry. They can be found in flour, cookies, dog food and pasta among other things. Adults which fly are pollen feeders. Perhaps your fabric softener is attracting them to the clothes. Check your dry goods and try to track down the source of the infestation.

Letter 4 – Pantry

 

Hello there,
I came upon your site by accident trying to identify a species of moth that’s been living with me. I just moved into a new apartment a few months ago and noticed that there were several moths in the apartment. I have no picture, but they are small, maybe 1/4 inch long, and very thin – they look a lot like a tiny segment of a stick. The head end tapers down slightly narrower than the wingtips. They are a mottled dark brown colour. They tend to sit on walls for long periods of time very still and only fly away when approached. Their style of flying is erratic and fluttery. I found a dead one in my pancake mix and the mix itself had a sour smell to it. I also found a small larva about the same size as the moth, white with an orange head, hiding under my teapot. I’m not sure if this was a larva of the moth or something else, though. These moths tend to hang out in the kitchen, so I have a sneaking suspicion that they may be after food. In some corners under or inside the cupboards I have found dead (or possibly the molted skins of) moths attached to the corner within a thin layer of silk. Any ideas on what these are, and if they are bad to have in the house?
Thanks,
Catherine

Hi Catherine,
You have pantry moths which will infest all types of grain products in the pantry, hence the appearance in the pancake mix. The larvae do the damage by devouring the foods. Mature moths will lay new eggs and the infestation perpetuates. Clean out the pantry and store drygoods that you
are not going to use immediately in a tightly sealed container (though this does not prevent eggs that have already been laid from developing) and better yet, refrigerate or freeze flour products. Do not stockpile drygoods when you have a potential problem in the pantry.

Letter 5 – Pantry

 

Yellow-green worm
Dear What’s That Bug,
We live out in the country in central Texas (30 minutes northeast of College
Station). When I went to change the sheets on my extra bed last night, I
discovered HUNDREDS of tiny yellow-green worms that had reproduced there
since I last changed the sheets (1-2 months ago). They were about about an
inch long (inch worm?). We hang our sheets outside in a wooded area and are assuming they came in with the sheets and multiplied like crazy. Do you know what they are. There were little caccoons in the bed folds, pillows, etc. Could they still be in the mattress!?! Being a city girl myself, I’ve adapted to the wide variety of spiders and roaches surrounding our house, but this has made me reach my limit! Your help would be greatly appreciated. What a great service you have!
Thanks!
Caren George

Dear Caren,
I must say, this is confusing. What you are calling worms are probably the larval form of some insect. Two common household pests that will eat organic matter, including cotton, are carpet beetles and clothing moths, but neither have larvae that are yellow green. You also didn’t state that the sheets had been damaged in any way, so I am eliminating them as possible culprits. There is no way that your free-loaders grew and reproduced between the sheets without eating. I suppose it is possible that they migrated there in search of a warm place to metamorphose, but that still doesn’t give me a clue as to what they might be. I will continue to research and hopefully get back to you when I discover something. Additionally, Inchworms are actually the caterpillars of a group of moths known as geometrids, and they get their name from their curious method of locomotion which has the
appearance of measuring.
Daniel

Mystery Solved
Dear Bugman,
We came home last night to more little worms (only a handful this
time)–even though we bleached and washed the sheets and cleaned the room completely. We tore down the bed and found the nasty culprit. A storage bin of cat food my husband had put under the bed. It was COMPLETELY webbed and gross and the bin was full of little moths. Looked on your site and was able to identify Indian Meal Moths! We emptied the room, cleaned EVERYTHING and put it back together again. I’ll write again frantically if that didn’t solve the problem! Thank you so much for your service and getting back to me. This city girl needs all the help she can get!
Sincerely,
Caren George

Authors

  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

    View all posts
  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

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Tags: Grain Beetle

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2 Comments. Leave new

  • I just moved to Oahu and these exact bugs are all over the 2nd floor of my house. I, too, have been scouring the internet and the closest picture I could find was the Xylopsocus castanoptera or Xylopsocus twig borer. But, your pictures look exactly like the ones in my house. They only come in at night and since the windows here are like shutters and the screens have gaps, they just come right in. They seem impervious to bug spray or foggers. I didn’t realized they could fly until recently. They don’t seem to be attracted to anything in particular since there’s no food up here. There are tons of fruit trees surrounding my bedroom windows, so that must be what they are are hanging out up here for.

    Reply

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