Flies with Long Legs: A Concise Guide to These Intriguing Insects

Long-legged flies are fascinating insects that catch our attention with their distinct appearance. One common example is the crane fly, which resembles a giant mosquito due to its slender body and extremely long legs. Although they may look intimidating, these insects are actually harmless and often found around water sources.

Crane flies are part of the fly family Tipulidae and come in a wide range of sizes, from tiny to almost 1.2 inches long. They are known for their slow-flying nature and fragile legs. Though these flies have a proboscis, they do not bite and are in fact non-threatening to humans.

In North America, there are hundreds of species of crane flies, all with unique characteristics. Their single pair of wings is usually held out at a 45-degree angle to their body, while small, antennae-like appendages called halteres help maintain balance during flight. Knowing more about these intriguing insects can help us better appreciate the vast diversity of creatures in our natural environments.

Understanding Flies with Long Legs

Distinguishing Features

Flies with long legs can be easily identified by their distinct appearance:

• Long, slender legs
• Metallic colors such as red, tan, blue, gold, black, copper, and metallic green
• Clear wings
• Unique antennae

Common Species

There are various species of long-legged flies in North America, including:

1. Dolichopodidae: Also known as “dancing flies,” these metallic insects are common throughout the continent.
2. Tipulidae: Commonly known as “crane flies,” they often have a tan or black body with long legs.

Habitat and Range

Long-legged flies can be found throughout North America and thrive in diverse habitats:

• Dolichopodidae: Predominantly found in wet, marshy areas, and forests with decomposing vegetation.
• Tipulidae: Mostly live in moist environments, such as streams, ponds, and wetlands.

These insects play a vital role in the ecosystem, preying on smaller insects and serving as a food source for larger animals.

Life Cycle and Behavior

From Egg to Adult

Long-legged flies, belonging to the family Dolichopodidae, undergo a complete metamorphosis which includes egg, larva, pupa, and adult stages. The time it takes to complete the life cycle varies depending on the species and environmental factors.

• Eggs: Females lay their eggs in specific habitats, such as soil, leaf litter, or decaying organic matter.
• Larvae: Also known as maggots, the larvae have several instars stages and consume a variety of organisms, including aphids, mites, and other small insects.
• Pupae: After the final larval stage, the larvae form pupae, which act as a protective case during the critical transition to adulthood.
• Adults: Adult long-legged flies emerge and begin to search for food and mates.

Feeding and Prey

Long-legged flies are predators, feeding on a variety of small insects such as:

• Aphids
• Mites
• Gnats
• Mosquitoes

Adults have been observed catching their prey in mid-air or plucking them off surfaces. They can also feed on nectar, while larvae typically consume other arthropods and decaying organic matter.

Reproduction

Males and females engage in mating behavior, often involving complex displays and rituals. Some key points about their reproduction include:

• Females require a blood meal before laying eggs.
• Eggs are typically laid in moist organic matter or soil.
• One female can lay up to 200-400 eggs at a time.

Pros of long-legged flies:

• Help control populations of pest insects.
• Act as pollinators when they feed on nectar.
• Contribute to maintaining a balanced ecosystem.

Cons of long-legged flies:

• Can be a nuisance if found in large numbers.
• Occasionally feed on beneficial insects.

Ecological Role and Benefits

Predators and Prey Relationships

Flies with long legs belong to the order Diptera and play a significant role in balancing ecosystems. They can be both predators and prey to other animals. For example, they feed on:

• Aphids
• Scales

These arthropods, in turn, become food for:

• Birds
• Bats
• Larger insects

Pollination and Plant Support

Long-legged flies are essential for pollination, as they are attracted to plants with open structures and white flowers. This helps improve gardening efforts and, in turn, supports wildlife and native plant growth. Some benefits of pollination include:

• Increased seed production
• Enhanced fruit and vegetable growth
• Improved meadow and garden ecosystems

Beneficial Insects in the Garden

Long-legged flies play an indirect role in supporting garden ecosystems. They help break down organic matter, releasing nutrients back into the soil. Moreover, they provide biological control of pests, thus contributing to overall garden health. Key pros and cons of having long-legged flies in the garden include:

Pros

• Natural pest control
• Adding balance to the ecosystem
• Pollination support

Cons

• Possible annoyance to humans
• Potential parasite transmission (rare)

Comparison table

In conclusion, long-legged flies positively impact garden ecosystems by acting as both predators and prey, pollinating plants, and helping maintain balance in the garden.

Managing Flies with Long Legs

When They’re Pests

• Crane flies belong to the family Tipulidae and are commonly mistaken for mosquitoes due to their appearance. However, unlike mosquitoes, these long-legged insects do not bite humans or pets [^1^].
  The crane flies’ larvae, known as leatherjackets, are known to cause damage to the roots of grasses, especially in damp meadows and lawns [^2^].Their habitat preferences often include fields, water margins, and woodlands.
• Daddy long legs, or harvestmen, are not true flies but rather belong to the arachnid family. They are not known to cause significant harm to plants or humans, but their presence can be alarming to some [^3^].

When They’re Beneficial

• The long-legged fly family (Dolichopodidae) is a group of metallic, brightly-colored flies that are predators of small insect pests such as aphids, thrips, and caterpillars [^4^]. They are commonly found near water sources, tree bark, and grassy areas.
• Crane flies also have some beneficial qualities. Their larvae can be food for fish, aquatic insects, and birds, while adults can help pollinate flowers and aerate the soil [^5^].

Comparison Table:

In summary, while some long-legged flies can be pests, others can be beneficial to the environment. It’s important to properly identify the species before taking any action, especially when considering the use of insecticides or other control methods in your yard or landscape.

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 – Crane Fly from Canada

Subject: Crane Fly
Location: Langley BC Canada
May 30, 2017 12:18 pm
Hey bugman just wondering what she is. I know it’s a crane fly, I believe it is a Nephrotoma. From the images I’ve found it looks like a Crocata to me. I live in BC Canada. I’m not really knowledgeable on insects, just curious as I’ve never seen on of these in my life.
Signature: Thanks

Wikipedia has an image of Nephrotoma crocata, and it does resemble your individual, but that is a European species and to the best of our knowledge, it has not been introduced to North America, but that is always a possibility.  We are more inclined to believe that you have an image of a native species in the subfamily Ctenophorinae which is pictured on BugGuide.

Letter 2 – Crane Fly artfully photographed

Odd Little Critter
Hey Bugman!
While hiking this morning I ran across this guy, I immediately thought of you (well, after I couldn’t mentally place it in my peterson’s guide [that’s in storage]). Any Ideas?
Chad

Hi Chad,
Your photograph of a Crane Fly is so artful. It really seems voyeuristic.

Letter 3 – Crane Fly

WHAT IS IT!!!!!!!!!!
Hi Bugman,
This is Bryce again Freshman of Kittson Central High in northwestern Minnesota. I like to lure bugs close to the house with a light and found what I assume is a Phantom Cranefly, but IT’S ENORMOUS. I put a ruler by it to show you it’s true size. Bryce

Hi Again Bryce,
Yes this is a Crane Fly, probably genus Tipula. Our Audubon Guide says they grow to 2 1/2 inches and yours is considerably larger. This is not, however, a Phantom Crane Fly which has distinctive black and white markings.

Letter 4 – Crane Fly

Hi, Bugman….
This guy was just stumbling around on the trunk of my avacado tree….having trouble finding his legs…..he couldn’t fly but he flapped his wings…. I’ve seen a lot of these…..this one was maybe newly hatched and just getting started….he wasn’t as big as the ones who used to live in my bathtub at my old place.
Anyway, this guy was just about an inch long, not counting his legs.. What is he? He looks just like a super sized mosquito, but friendlier, and not at all bloodthirsty. Thanks…..Jonathan

Dear Jonathan,
How nice to hear from you.
You’ve got a common crane fly, (Tipula planicornis). The larger species is the Giant Crane Fly (Holorusia hespera) which can have a three inch wingspan. Craneflies have short soft mouthparts and are incapable of biting. Larvae are called leather jackets and are found in rotting vegetation. Some are aquatic.

Letter 5 – Crane Fly

Can you help me identify this bug?
October 20, 2009
Found and took a photo of this bug with long legs, wings and a pointy rear end. Can you please identify him for me? Thank you.
Alex Tosh
Presidio, San Francisco, CA

Hi Alex,
This is a nice detailed image of a Crane Fly.  They are harmless.

Letter 6 – Crane Fly

Unknown Fly (?) in Ann Arbor, MI.
April 24, 2010
Hi Bug Identifiers!
I was kicking around in my yard today, taking some pictures, and I found this interesting fly. It was walking on the leaf litter, and, when I knelt to take some photos, it held very still until I was done. I’ve looked at the flies in your fly section, but I didn’t see anything that looked much like it.
Stephen
Ann Arbor, Michigan, USA

Hi Stephen,
This is a Crane Fly, but unless they are really distinctive looking, we have great difficulty identifying Crane Flies to the species level.  A great place to begin if an exact species is important for you, is the Crane Flies of Pennsylvania website of the Carnegie Museum of Natural History.  Chen Young will respond to your identification requests.

Hi Daniel,
Thanks very much for the response. After I sent you the request for identification, I spent about two hours digging around bugguide and some other websites. It looks like it may be nephrotoma pedunculata.
Thanks again,
Stephen

Hi again Stephen,
We don’t really see the resemblance between your individual and the Nephrotoma pedunculata posted on Bugguide.  We like Hexatoma spinosa as a better match.  The Crane Flies of Pennsylvania indicates:  “Hexatoma spinosa are about 16 (male) – 28 (female) mm in body size and the males are characterized by having antennae of about 28 mm in size and are approximately three times the length of the body.   The males often form large mating swarm near the margins of streams.“ That means the photo of the living specimen on the site, which is the same photo on BugGuide, is of a male and your specimen would be a female.  We are going to contact Chen Young for a confirmation.

Ed. Note: We received an “out of office” reply to our email to Chen Young, so a confirmation here will have to wait.

Ed. Note:  Chen Young replies
April 30, 2010
Hi Daniel,
I think this is a Tipula (Lunatipula) dorsimacula.  http://iz.carnegiemnh.org/cranefly/tipulinae.htm#Tipula_(Lunatipula)_dorsimacula
I am out of country now and can do much to confirm but with the dorsal color I am pretty sure it is T. dorsimacula.
Thanks,
Chen

Letter 7 – Crane Fly: Ctenophora dorsalis

Subject: What is this thing?
Location: Bangor, Pennsylvania
June 2, 2013 6:10 pm
Hi,
I found this crawling around my yard today. At first glance I thought it might be a wasp. But I’m pretty certain its’ not. I’ve done quite an exhaustive search online using obvious keywords w. no luck.
Sorry for the slight blur, this alien would’t sit still!
Hope to get an I.D.
Thanks!
Signature: Paul C.

Hi Paul,
Sorry for the delay.  We were away from the office for ten days and we are randomly selecting from the 100s of unanswered requests we have received in a feeble attempt to make a dent in our inbox.  This is a female Crane Fly, Ctenophora dorsalis, which we identified on BugGuide.