Narcissus Bulb Fly: Essential Tips and Facts

The Narcissus Bulb Fly is a pest that can cause significant damage to flowering bulbs, particularly those in the Narcissus family. These flies, scientifically known as Merodon equestris, bear a striking resemblance to honey bees or bumble bees due to their hairy yellow or orange-brown bodies 1. Being aware of their appearance and life cycle is essential in order to effectively prevent and manage infestations.

Adult Narcissus Bulb Flies typically emerge from the soil during May, where they mate and lay their eggs near bulbs 2. Once the eggs hatch, the larvae burrow into the bulbs and feed on their insides. This leads to the destruction of bulb scales and flower parts, as well as impeding the growth of healthy leaves and flowers. In some cases, infested bulbs may only produce grassy-looking leaves 3.

Narcissus Bulb Fly Identification

Adults

The adult narcissus bulb fly, scientifically known as Merodon equestris, is a heavy-bodied fly that mimics the appearance of bumble bees ¹. Some key features of adult bulb flies include:

• Sizes ranging from 3/8 to 1/2 inch
• Hairy bodies
• Variable colors from reddish-brown, orange, or tan ²

Larvae

The larvae or maggots of the narcissus bulb fly exhibit the following characteristics:

• Plump and wrinkled bodies
• Grayish-white to yellow color
• Length ranges from 1/16 inch when newly hatched to 3/4 inch when mature ³

Eggs

Narcissus bulb fly eggs can be identified by their presence and location:

• Females typically lay one to three eggs [|4|]
• Eggs are laid on leaves near the soil surface or on the crowns of narcissus plants ⁴

Life Cycle and Biology

Emergence

The Narcissus bulb fly emerges from the soil in May. The adult fly is about 1⁄2″ long and closely resembles a small bumblebee.

Feeding and Development

• Female lays eggs near bulbs in early summer
• Hatching maggots burrow into the bulbs and feed inside
• Larvae are plump, white to yellow, and wrinkled
• Length: 1/16 inch when newly hatched, ¾ inch when mature

The feeding larvae cause significant damage to the bulbs, often leading to bulb destruction. Narcissus (daffodils) bulbs are particularly badly damaged by the Narcissus bulb fly.

Comparison of Bumblebee and Narcissus Bulb Fly:

Pupation and Overwintering

After feeding and development throughout the summer, larvae pupate in the soil to overwinter. The cycle begins again the following May when new adults emerge from the pupae.

Infestation and Damage

Host Plants

The Narcissus Bulb Fly primarily infests bulbs of:

• Narcissus (daffodils)
• Hyacinth
• Iris
• Amaryllis
• Galanthus (snowdrop)
• Hippeastrum
• Nerine

Signs of Infestation

Keep an eye out for:

• Adult flies resembling small bumblebees, about ½” long
• Female flies laying eggs near bulbs in early summer
• Grassy-looking leaves, potentially indicating infested bulbs¹

Impact on Bulbs

Narcissus Bulb Flies have the following impact on bulbs:

• Larvae (maggots) burrow into bulbs near the basal plate
• Feed inside the bulbs, destroying scales and flower parts
• Infested bulbs produce a few, grassy-looking leaves or develop rot²

Prevention and Management

Cultural Practices

• Healthy bulbs: To prevent Narcissus Bulb Fly infestation, start by selecting healthy and disease-free bulbs for planting.
• Planting: Plant bulbs in well-drained soils to discourage the larval growth and avoid overwatering.
• Mowing and cultivating: Regularly mow and cultivate the area around the bulbs to minimize hiding spots for adult flies.

Chemical Control

• Insect netting: Protect your plants with insect netting to keep adult flies away from the bulbs.
• Insecticides: Although many chemical options have been removed from the market, you may still find some available. Consult your local extension service for recommendations that suit your region.

Comparison of methods:

Pros and cons of chemical control:

• Pros

  • Quick results in pest reduction
  • May be necessary in severe infestations

• Cons

  • May harm beneficial insects
  • Potential for development of insect resistance

Remember, a combination of these methods may work best to prevent and manage Narcissus Bulb Fly infestations in your garden. Consult with your local extension service if you need further guidance.

Frequently Misidentified Insects

Narcissus bulb fly, which refers to two species – the large narcissus fly (Merodon equestris) and the small narcissus fly (Eumerus strigatus) – often gets misidentified due to their resemblance to certain bees. They get mistaken for bumble bees, but there are key differences that can help identify them correctly.

Both large and small narcissus flies display yellow or brown markings on their bodies similar to those on bees. However, they belong to the fly family and are classified as dipterans. A comparison of their features can assist in distinguishing them:

Bumble Bees:

• Have two pairs of wings
• Exhibit pollen baskets on their hind legs
• Possess a straight antennae

Large and Small Narcissus Flies:

• Have only one pair of wings
• Lack pollen baskets on their legs
• Possess a distinct L-shaped antennae

Example: A gardener might mistake a large narcissus fly (Merodon equestris) buzzing around their narcissus plants for a bumble bee, owing to the fly’s yellow and black banding on its body.

While the large narcissus fly predominantly damages narcissus bulbs, the smaller species of bulb flies like Eumerus strigatus are associated with several bulb crops, including Allium.

In conclusion, it’s essential to keenly observe the features of the insects around your garden to ensure their accurate identification. Doing so aids in the effective management of pests, thereby protecting your plants from any potential harm.

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 – Male Narcissus Bulb Fly from UK

Subject: a bee or a beetle!?
Location: County Down, Northern Ireland
May 15, 2014 5:30 am
Hey bugman! Me and my mum were just digging through some soil in our garden and found this weird looking insect! It’s body is all fuzzy and the colour of a bees but the head area is a yellow coloured shell? And it’s wings are very tiny and at the side of it! Also it’s eyes are like something you’d see in a cartoon of a house fly (really big and buggy). You can also clearly see wee pinchers for it’s mouth! I’ve never seen a bee or anything like this and it’s also weird that it was found in soil.
Signature: Many thanks, Rosalyn

Hi Rosalyn,
This is neither a bee nor a beetle, but you were on the right track when you noticed its eyes resembling those of a house fly.  This is a Fly in the order Diptera, and the fact that you found it underground indicates an underground pupation.  The wings have still not expanded after it emerged from the pupal stage.  The color and furry body are quite distinctive, and our first clue was images of a Narcissus Hoverfly, Merodon equestris, on UK Safari, however, the images there show very different eyes.  The site indicates:  “look like small bumblebees” and “The ‘Narcissus’ name is given because they lay their eggs on Narcissus plants (daffodils).  When the eggs hatch, the larvae burrow down into the plants to feed on the fleshy bulbs.”  Everything seemed to fit but the shape of the eyes.  The eyes on your individual meet at the front of the head, so we continued searching.  On Bugs and Weeds, we learned that the Large Narcissus Fly:  ” only survives for a short while – between 5 and 24 days, and lays its eggs low down on the leaves of daffodil, narcissus and bluebell plants. On hatching the larvae make their way down into the bulb where they will feed for something like 300 days before re-emerging to pupate in the soil.”  We began to ponder the possibility that like Horse Flies, the Narcissus Hoverfly might exhibit sexual dimorphism, with the spacing between the eyes helping to distinguish the sexes.  That proved to be correct when we finally located an image of a male Narcissus Hoverfly on RI Bugs where it is called a Narcissus Bulb Fly.  Once we realized that the Narcissus Bulb Fly was also found in North America, we searched BugGuide and located another matching image of a male that matches your individual, except for the wings, which we have already indicated have not expanded to their full size in your image.  We are speculating that you have daffodils planted near the site of the sighting.  

Letter 2 – Mating Narcissus Bulb Flies

Subject: Loving Bee Flies
Location: Andover, NJ
May 27, 2015 12:36 pm
Hoping you can narrow down an id on these bee mimics. I’m in northwestern NJ and have been seeing these around my garden for the last few weeks. This pair was making a very loud buzzing sound and stayed joined for at least 5 minutes before separating and buzzing off. At one point I eased them off the steps and onto a leaf, then transferred them to some flowers, hoping to get a better camera angle. I am thinking they are some sort of hoverfly?
Signature: Deborah Bifulco

Dear Deborah,
We believe these are mating Narcissus Bulb Flies, Merodon equestris, which are in the Hover Fly family Syrphidae, not the Bee Fly family Bombyliidae, though we may be wrong.  You can verify our identification by comparing your images to those posted to BugGuide.

Thanks, Daniel!  As always, you’ve been a great help.
Debbi

Letter 3 – Narcissus Bulb Fly

Subject: Bee? Fly? Friend or Foe?
Location: TN
February 27, 2015 8:47 am
I’m hoping someone can help me identify this bug. I’ve found 3 of them thus far. They appear to have been created in my large pot of amaryllis that I drag indoors and outdoors each year. Last fall, I quit watering the large pot and stored it in cool, darkish conditions (unheated garage) for about 4 months. After moving it to a warm sunny location – these gentle creatures are making their appearance. Google hasnt helped. Thanks for any information you can share!
Signature: Green thumb – newbie apridarist

Dear Green thumb-newbie apridarist,
This is a Narcissus Bulb Fly, Merodon equestris, which we identified on BugGuide, and though they are generally associated with daffodil and narcissus bulbs,  according to the North Carolina State University Insect and Related Pests of Flowers and Foliage Plants site:  “Distribution -The narcissus bulb fly occurs wherever narcissus are grown throughout the United States. This pest was introduced from Europe in about 1869.  Host Plants -The narcissus bulb fly has been reported to infest amaryllis, daffodil, Galtonia, Flanthus, hyacinth, Iris, lilies, Leucofum, Narcissus, Scilla, tulips, and Vallota.  Damage -The center of the bulb is hollowed out and the flower bud is destroyed. Many infested bulbs rot away although some survive to send up a few scrawny grasslike blades the following year.”

Letter 4 – Narcissus Bulb Fly

Subject: Fuzzy Fly? on Eschscholtzia in garden
Location: Pleasanton, CA
April 15, 2015 7:28 pm
I would appreciate it if you could help identify this insect. It looks like an orange, fuzzy fly, about the size of a small bumblebee. It was visiting my garden in early April, and though I have looked for it many days since, that first day was the only time I’ve seen it.
Signature: R. Battaglia

Dear R. Battaglia,
Your request has been sitting on our back burner since we first read it, because we recognized this fly, but we couldn’t remember its name.  Today it hit us.  This is a male Narcissus Bulb Fly, Merodon equestris, a member of the generally considered beneficial family Syrphidae, the Flower Flies or Hover Flies.  According to BugGuide it is:  “native to Europe, adventive and now widespread in North America (wherever Narcissus are grown), Japan, and Australasia Food Larvae live in and feed upon plant bulbs.”  Your individual looks exactly like this image posted to BugGuide.

Letter 5 – Narcissus Bulb Fly from Alaska

Subject: Bee fly of some sort?
Location: Anchorage, Alaska
July 21, 2017 8:12 pm
Found this guy on my deck in Anchorage, Alaska. He didn’t seem to be doing so well.
He doesn’t look like any sort of fly or bee I’ve seen around here.
Signature: Friend of Bees

Dear Friend of Bees,
We verified the identity of your Narcissus Bulb Fly with this BugGuide image.  According to BugGuide:  “native to Europe, adventive and now widespread in North America (wherever daffodils (Narcissus spp. are grown), Japan, and Australasia” and “Larvae live in and feed upon plant bulbs; adults nectar widely.”

Thank you very much. I don’t have narcissus bulbs, but my neighbors do. I’ll make sure she checks her bulbs this fall.

Letter 6 – Narcissus Bulb Fly from England

Subject: ?Beefly
Location: Salisbury, UK
June 2, 2012 6:08 am
Dear Bugman,
I encountered this insect in a garden in southern England on 2nd June 2012. weather was bright but not sunny, the fly seemd lethargic and unwilling to fly. It was sitting on some aubretia. I have included a second image to show the folding of the wings, one on top of the other. Can you enlighten me please
Signature: Rich

Hi Rich,
This furry bee mimic had us perplexed, and we thought it resembled a Bot Fly, so we did some searching and found several similar looking Bot Flies in the UK and Europe, including the Deer Bot Fly, Cephenemyia auribarbis, which we found pictured on the Natural History Travel Notes Blog and this related species on Wikipedia.  Though they were similar, they were not an exact match, so we sought assistance from Eric Eaton who replied:  “Hi! No, this is the Narcissus Bulb Fly, Merodon equestris.  It is a type of syrphid fly.  Eric”  We then found a matching photo on Garden Stew and a nice description of its life cycle on the North Carolina State University website.  We will be away for a week beginning next week and we are postdating your identification request to go live on our website during that time.

Daniel,
You guys are great. That figures, I have lots of narcissi in my garden, obviously being eaten to hell!! Thanks so much, I’ll make a donation shortly.
Rich

Thanks Rich.  The Garden Stew website offers this gardening advice:  “A little tip to help is that when you pull out the leaves or flowers, run your hand over the soil to fill in the holes. These holes give the fly access to the bulbs. “

Letter 7 – Narcissus Bulb Fly from Netherlands

Is this Merodon equestris var. equestris?
May 4, 2010
I am pretty sure that this is Merodon equestris and I WAS pretty sure that it is variation equestris, but I read somewhere that this species ALWAYS has black legs.
Mine has whitish blots on it’s legs (and the wing veins seem lighter than those on specimens I found images of on the internet).
Can you help me out?
Thanks in advance 🙂
Enmos
The Netherlands

Dear Enmos,
WE were not familiar with this species, so we checked BugGuide.  Merodon equestris, the Narcissus Bulb Fly, is listed on BugGuide, but its origin is not listed.  Wikipedia indicates it is European.  BugGuide indicates a vein pattern that resembles a sock, but alas, none of your excellent images shows this feature.

Sadly, we haven’t the time at the moment to research the subspecies.  YOur excellent images are a wonderful addition to our site.