Grass Carrying Wasps Facts

In this article, we will try to cover all aspects of the grass carrying wasps, their habitat, what they eat, how they reproduce, and more.

Flying insects that build nests can often be a nuisance to homeowners.

If you find a bug nest in a window frame made of dried grass, it might be the handiwork of a grass carrying wasp.

While these wasps aren’t very dangerous, having them buzz around or build nests in inconvenient spots can be a bit annoying.

Let’s find out more about this interesting wasp species and how to deal with it.

Grass Carrying Wasp

What Are Grass Carrying Wasps?

Grass carrying wasps get their name from the fact that they are often spotted flying around with blades of grass.

More specifically speaking, it’s the females that display this unusual behavior, using tall grass to build their nests.

They are a species of thread-waisted wasps (Sphecid wasps), growing up to a length of 0.75 inches with a shiny black body.

You might want to note that grass carrying wasps are a solitary insect species, which means they build small nests and live by themselves rather than living in a colony.

What Does A Grass Carrying Wasp Eat?

Like most wasps, adult grass carrying wasps primarily feed on nectar and pollen.

Among native plants, they are especially attracted to mountain mint, rattlesnake master, boneset, and goldenrod.

The females also prey on insects, especially tree crickets and katydids. However, they do not feed on these insects themselves.

They paralyze the prey and drag them into the nest, to serve as food for the newborn grass carrying wasp larvae when the eggs hatch.

Grass Carrying Wasp

Where Do Grass Carrying Wasps Live?

Contrary to most Sphecid wasps, grass carrying wasps do not burrow underground. Instead, they mostly use aboveground cavities like hollow stems to build their nests.

They might, however, use pre-existing holes in the ground for this purpose. They’re often found to build nests in suitable indoor spots too, especially in door and window tracks.

It’s easy to mistake a grass carrying wasp nest for a random lump of dry grass that made its way to your home with the wind.

The grass nests may either have several brood cells partitioned by blades of grass, or a single communal area where all the larvae stay, feed, and develop.

The Lifecycle of a Grass Carrying Wasp

The life cycle of a grass carrying wasp isn’t very different from that of other common solitary wasps.

They go through the four life cycle stages typical of insects – egg, wasp larva, pupa, and adult.

Eggs

These wasps produce only one generation a year, or two at most. The eggs are laid in the grass nests they build. Adult female grass carrying wasps provision their nests with paralyzed insects for the offspring.

Larvae

The larvae hatch in a few days and spend the next week or so feeding on the cached prey. They molt during this time, developing and growing in size.

Pupae

Once the larvae have exhausted the food stored in the nest, they spin a cocoon around themselves.

They overwinter in their cocoons, either in a pupal or pre-pupal state, depending on their stage of development at the time of cocooning.

The wasp resumes development in the spring, eventually ending the pupal stage and emerging as an adult wasp.

Adults

Grass carrying wasps spend most of the adult stage of their life cycle foraging for pollen and nectar.

The females begin constructing their nests soon after mating, which is when you’d find them carrying blades of grass.

Once the nest is ready, the adult female wasp will start hunting in high canopies in search of prey, which she paralyzes and carries to her nests.

She lays her eggs once the nest is well-stocked with food.

Grass Carrying Wasp

Do They Bite/Sting?

Grass carrying wasps aren’t much of a threat due to their non-aggressive nature. Despite being stinging wasps, they’d sting you only if you made them feel provoked or threatened.

Unlike social wasps, they live alone and don’t have a colony to defend.

This significantly lowers the chances of getting stung because you got too close to a grass carrying wasp nest.

Grass carrying wasps are comparable to digger wasps in this aspect. As long as you leave them alone, they will do the same for you.

Are They Poisonous/Venomous?

Being a parasitoid wasp species, grass carrying wasps carry paralyzing venom that they use to immobilize their prey.

Don’t get worried, though; the venom is too weak to have any effect on humans. Besides, they don’t use the venom on anyone besides their prey anyway.

Are They Harmful or Beneficial to Humans?

Despite the general notion that wasps are dangerous, most of them are beneficial insects. The grass carrying wasp is no exception either.

Firstly, grass carrying wasps are amazing pollinators. Farmers often lure them to their gardens or agricultural fields by providing nesting places.

Secondly, these black wasps also help control pest populations by hunting them down to provide food for their larvae.

What Are Grass Carrying Wasps Attracted To?

Since adult grass carrying wasps feed primarily on pollen and nectar, they are attracted to flowering plants. As mentioned earlier, they have a preference for certain flowers like goldenrod, mountain mint, boneset, etc.

You may also attract them to your garden by installing bee hotels or simply digging small holes where they can nest.

Grass Carrying Wasp Nest

Removing Grass Carrying Wasps

There’s no need to get rid of grass carrying wasps unless the nest location is causing you inconvenience or puts you at risk of getting stung.

If you must remove grass carrying wasps from your property, simply removing the nest should usually be enough.

It warns the wasps that the spot is unsafe for nesting, prompting them to go elsewhere.

If they are persistent and keep returning, you may consider using a pesticide. However, stick to low-toxicity pesticides that are safe for residential use.

Interesting Facts About Grass Carrying Wasps

Before we conclude this article, here are some interesting tidbits about grass carrying wasps.

• Despite being capable of delivering a painful sting, these wasps are generally harmless to humans.
• Unlike most solitary species of wasps, grass carrying wasps don’t usually build their nests underground.
• These wasps are native to North America, which means there’s a good chance that you might come across them.

Wrapping up

Though social wasp species like paper wasps and yellow jacket wasps are feared due to their aggressive nature and painful stings, the grass carrying wasp is nowhere near as dangerous.

They are more like female digger wasps—harmless unless you bother them.

So, the next time you see a wasp carrying a blade of grass or tucking it into a hole, there’s no need to panic. Thank you for reading, and I hope you found this article helpful.

Grass Carrying Wasp Nest with Crickets

Frequently Asked Questions

Why are wasps flying around my grass

There could be various reasons why wasps are flying around your grass. One reason could be that there is a nest nearby, and the wasps are searching for food or gathering materials to build their nest.
Another reason could be that there are flowers or plants in your grass that are attracting the wasps.
Wasps are also attracted to sweet and sugary substances, so if there are any spilled drinks or food in the area, the wasps may be attracted to it.
It is important to be cautious around wasps as they can sting and cause allergic reactions in some people. It is best to avoid disturbing any nests and to keep food and drinks covered when outside.

What are some fun facts about common wasps?

Common wasps, also known as yellow jackets, are one of the most aggressive species of wasps.
They are known for their painful stings, which can be life-threatening to people who are allergic to their venom. However, there are some fascinating facts about these insects.
For example, yellow jackets are social insects that live in large colonies. The queen wasp is the only one who lays eggs, and the other members of the colony are responsible for feeding and protecting the queen and her offspring.
Yellow jackets are also known for their love of sweets, and they are often seen buzzing around picnic tables and garbage cans in search of sugary treats.
Interestingly, yellow jackets are not always yellow; some species have black and white markings, while others have red and black stripes.

What do wasps fly around looking for?

Wasps fly around looking for food and nesting material. They are carnivorous insects and feed on other insects, spiders, and some sugary substances like nectar and fruit juices. In the late summer months, wasps become more aggressive in their search for food, as they need to stockpile enough food to survive the winter. Wasps also fly around looking for suitable places to build their nests. They prefer sheltered areas such as under eaves, in attics or sheds, or in trees and bushes. Once they find a suitable spot, they will start building their nests using materials like chewed-up wood fibers, mud, and saliva.

What is the meaning of wasp nest?

A wasp nest is a structure created by social wasps to house their colony. It is typically made of a paper-like material that the wasps create by chewing wood and mixing it with saliva. The shape and size of the nest can vary depending on the species of wasp, but they are usually round or oval and have a small entrance hole. Wasp nests can be found in a variety of locations such as trees, bushes, eaves of buildings, and underground. While wasp nests can be fascinating to observe, it’s important to exercise caution as wasps can be aggressive and their stings can be painful or even deadly for those who are allergic.

Reader Emails

Grass-carrying wasps are quite abundant in the United States. And cleaning up their cocoons from window sills is one reason why many of us become immediately aware of them.

Over the years, we have gotten many questions from our readers asking to learn more about these creatures. Please go through a selection of these mails below.

Letter 1 – Nest of a Grass Carrying Wasp

 

Subject: bug and nest material Location: Rochester, New York August 7, 2012 1:50 pm Hi. I keep getting bugs of some kind nesting between wood casement windows and the jambs…a teeny tight space. Sometimes I find clumps of dry grass, other times little dried mud tubes(maybe a different species). I’m amazed they can squeeze in there and can’t figure out what the attraction is. They aren’t damaging the wood, but messy when I open a window that’s been closed for months, and the stuff falls into the room. In today’s cleaning I found actual bugs (a brighter green than the photo shows). Thank you! Signature: Hiawatha

Grass Carrying Wasp Nest provisioned with Tree Crickets

Dear Hiawatha, The insects in your photo did not make this nest.  They are what appear to be Tree Crickets and they are the prey of the nest maker, a Grass Carrying Wasp in the genus Isodontia.  According to BugGuide:  “Larvae are fed Grillidae (particularly tree crickets) or other Orthoptera” and “These wasps commonly make their nest in the narrow track found above outer windows.”  See BugGuide for additional information on the Grass Carrying Wasp.  The mud nests you found were most likely the nests of Mud Dauber Wasps and they are generally provisioned with spiders to feed the larvae.

Grass Carrying Wasp Nest

Wow…thanks, Daniel!  That was a fast response and very comprehensive.  I really appreciate your taking the time to answer.  There’s probably nothing I can do to keep the grass carrying wasps out of the narrow track above the windows, but at least I know what I’m up against. Again, thanks very much, Jim Dierks Rochester, NY Hi again Jim, Neither Grass Carrying Wasps nor Mud Daubers are aggressive species and you should not fear getting stung. Good to know, Daniel.  Thanks.  I’ll just let the little guys do their thing, and with all the other troubles I’ve had with these windows, at least the wasps are just using some convenient space and not harming the windows at all. Regards, Jim Dierks

Letter 2 – Grass Carrying Wasp Nest

 

Subject: Found these guys nesting in our window… Location: Fort Mill, SC September 22, 2012 12:05 pm Hello! I am writing because I am really hoping you can help me figure out what on Earth these guys are. Last week I was measuring for a fire ladder and accidentally dropped the screen out of the window. I was showered with insect parts and nesting material. On top of the screen there was a straight line of these guys, and I am at a loss as to what they are. Each cocoon was about an inch long. Hoping you can shed some light on the situation! Signature: Thank you so much, Ashli Welsh

Grass Carrying Wasp Nest

Hi Ashli, You have discovered the nest of a Grass Carrying Wasp in the genus Isodontia.  According to BugGuide:  “Females make nests in a tree, hollow stem or other cavity, divide into sections and close with grass. They provision with Orthoptera (Tettigoniidae, Gryllidae)” and “These wasps commonly make their nest in the narrow track found above outer windows.”  The wings in your photos appear to be those of Tree Crickets which have been eaten by the wasp larva.

Grass Carrying Wasp Nest

 

Letter 3 – Grass Carrying Wasp Nest

 

Subject: Green insect Location: New Jersey July 4, 2016 5:15 am I have some type of insect nesting in my house window tracks. Have been seeing them for four years. This is the first time we have seen the actual insect. Signature: Paula

Grass Carrying Wasp Nest

Dear Paula, While you are correct that this is a nest, the green insects, which are immature Orthopterans, are not constructing the nest.  This nest was constructed by a Grass Carrying Wasp in the genus Isodontia, and the female has provisioned the nest with paralyzed Orthopterans, generally Crickets and Katydids, that serve as a fresh food supply for her developing larva which is visible on the far right of your image.  It is a whitish-gray grublike creature.  We frequently receive reports of Grass Carrying Wasps nesting in window tracks. Daniel, Thank you! How interesting! I do not know much about the Wasp at all. Is it OK to leave them to keep nesting in the track or will they somehow harm the window/house? I love your website and rely on it frequently for insect identification. Thanks for your quick response. Paula Truax

Letter 4 – Bug of the Month May 2017: Grass Carrying Wasps found in Home

 

Subject: Is this an ichneumon wasp? Location: Austin, TX April 30, 2017 8:49 am What is this bug? Finding them inside the house this spring trying to get out…hanging around the windows…do they sting/bite? Any house structure damage concerns? Signature: Stephen

Grass Carrying Wasp

Dear Stephen, Based on BugGuide images, we are pretty confident that this is a Grass Carrying Wasp, Isodontia mexicana.  According to BugGuide:  “Taken from the Internet Reference below (Penn State): The adult wasps emerge from their cocoons in early summer, mate, and the females locate a suitable nest site. She collects blades of grass and grass and hay stems to line the nest cavity. The wasp can be seen flying through the air with the blades trailing beneath her. She lands at the hole and enters, pulling the blade in behind her. After the nest is prepared, she hunts for tree crickets (i.e., Oecanthus sp.), captures and paralyses them with her sting, and transports them to the nest. She deposits eggs in the nest and the emerging larvae will feed on the living, but immobile crickets. When the larvae reach the appropriate size (in 4–6 days at 70–75° F.), they spin a cocoon and pupate. The adult wasps emerge in 2–3 weeks. In Pennsylvania, Isodontia mexicana typically produce two generations per year.  Remarks These wasps commonly make their nest in the narrow track found above outer windows.”  We have many more images in our archives of the nests of Grass Carrying Wasps because they are so frequently found in window tracks.  Solitary wasps are generally not aggressive, and rarely sting humans, though that possibility does exist.  Since they are harmless, and since it appears one individual in the images you attached might be dead from unnatural causes, we are tagging this submission as Unnecessary Carnage.  Because Grass Carrying Wasps are emerging from nests formed in window tracks now that spring has arrived, and because we suspect other homemakers might be experiencing similar sightings, we are tagging this posting as the Bug of the Month for May 2017.

Grass Carrying Wasp

Update:  Grass Carrying Wasps reported from France Subject: Grass carrying wasp July 25, 2017 5:29 am Looking at your excellent site, I think you may have resolved two mysteries for me. We have noticed recently a number of ‘grass carrying wasps’ around our dining table on the terrace. They have been disappearing into the metal frame taking their blades of grass with them. However, without taking the table apart we have been unable to tack where they are going. I assumed them to be carrying the grass for nesting material and your site confirms this. What you may have also answered is the reason why over the past couple of weeks, we have been finding a number small, bright green crickets on the chairs and the terrace around the table. Anything from 1 to about a dozen or so at any one time. We assumed them to be dead but your item on the  g.c.w. suggest that may not in fact be the case. If I may ask a question – we live in the south-west of France which is a long way from you folks. Can you confirm if these wasps are the same i.mexicana as you have or another entirely different insect altogether. Many thanks for creating and maintaining the website. I use it often. Have a nice day y’all. Robin PS – If I can get a decent photograph I will send it to you. Signature: Robin Nichols Dear Robin, We sometimes have a hard time with French sightings as there are not many comprehensive insect websites devoted to French species, however, folks in the UK seem to really like their bugs.  According to the Bee Keepers Garden:  ” A new to Britain wasp, Isodontia mexicana (de Saussure), known as the Grass-carrying wasp, has been discovered at Greenwich Peninsula Ecology Park. …  Researcher David Notton of the Natural History Museum said the wasp is pretty docile and a solitary species, so does not form large nests. ‘It’s quite unlike the better known and aggressive yellow/black social wasps with which people may be familiar.  We don’t know how it got to the UK, and although it’s a non-native invasive species there’s no evidence to suggest it’s a threat to UK fauna.'”  Since the Grass Carrying Wasp has been reported in the UK, it might have also been introduced to France.  According to Encyclopedia of Life:  “Isodontia mexicana, the grass-carrying wasp, is one of the thread-waisted wasps belonging to the family Sphecidae. It is native to North America, found east of the Rockies and through Central America, but has recently been introduced into France, where its population is slowly spreading through Europe.”  Good morning Daniel, Many thanks for your reply regarding the grass carrying wasp. I have since looked on the internet for information regarding the existence of the insect in France. According to a (French) Wikipedia entry the wasp arrived in southern France sometime during the 1960’s, since which time it has spread throughout the Midi region (effectively the southern half of France) and is now present in Italy, Spain and Switzerland. Helped, it is believed, by the long, countrywide heatwave in 2003, it managed to traverse the Massif Central into more northerly parts of France and is gradually spreading further north – presumably as global temperatures rise. I As you say, it has now also been found in the UK. Kind regards Robin

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