Robber Fly vs Wasp: Uncovering the Key Differences

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Robber flies and wasps might look similar at first glance, but there are some key differences between these two types of insects. While both are predators in the insect world, their physical features and behavior set them apart.

Robber flies, also known as assassin flies, are part of the Diptera order, which means they have two wings. These predatory insects have a long, tapered abdomen and a humpbacked appearance. Their legs are spiny, their face often appears bearded, and their mouthparts consist of a pointy, knifelike proboscis. These flies use their agile flying skills to catch their prey in midair. Species of robber flies vary in appearance, with some even mimicking the appearance of wasps and bees ([source)].

On the other hand, wasps belong to the Hymenoptera order, which includes bees and ants as well. These insects have four wings and a characteristic narrow waist that separates their thorax from their abdomen. Unlike robber flies, wasps build nests and can either be solitary or social. Their mouthparts are designed for biting and chewing, and they also possess a stinger for defense and hunting purposes.

Robber Flies and Wasps: An Overview

Classification and Appearance

Robber flies and wasps are both insects, but they belong to different orders. Robber flies (family Asilidae) are part of the order Diptera, while wasps belong to the order Hymenoptera.

  • Robber flies:
    • Medium to large-sized flies (3/8 to 1-1/8 inches)
    • Gray to black, sometimes mimicking wasps or bees
    • Hairy-bodied with a long, narrow, tapering abdomen
    • Examples: Assassin Fly, Robber Fly1
  • Wasps:
    • Varying sizes and colors
    • Distinctive narrow waist and two pairs of wings
    • Cylindrical abdomen with a stinger at the end
    • Examples: Paper Wasp, Yellow Jacket2

Comparison Table

Feature Robber Fly Wasp
Order Diptera1 Hymenoptera2
Family Asilidae1 Varies (e.g. Vespidae, Sphecidae)2
Abdomen Shape Long, narrow, tapering1 Cylindrical with a narrow waist2
Mimicry Mimics wasps and bees1 No mimicry
Sting No stinger, venomous saliva1 Stinger with venom2

Habitat and Range

  • Robber flies:
    • Found in various habitats, often on plants’ stems or the ground3
    • Known to live in the United States, including areas like North Carolina3
  • Wasps:
    • Live in diverse environments, often in nests built for protection4
    • Widespread throughout the United States, including North Carolina4

In both cases, they inhabit regions where they can easily find prey to feed on12.

Physical Adaptations

Wings and Flight

Robber flies:

  • 2 wings
  • Fast and agile in flight

Wasps:

  • 4 wings
  • Greater lift capacity

In terms of wings and flight, robber flies have two wings, which allows them to catch their prey with agility and quickness. Wasps, on the other hand, possess four wings providing them with greater lift capacity.

Eyes and Vision

Robber flies:

  • Large compound eyes
  • Excellent vision

Wasps:

  • Large compound eyes
  • Good vision, rely on warnings from colors

Both robber flies and wasps have large compound eyes, which provide them with strong visual capabilities. Robber flies have excellent vision, allowing them to spot and chase prey. Wasps also have good vision but rely more on warnings from colors, particularly when it comes to identifying potential predators.

Mouthparts and Feeding

Robber flies:

  • Piercing and sucking mouthparts
  • Predatory diet (including bees, wasps, and other insects)

Wasps:

  • Chewing mouthparts
  • Predatory and/or nectar-feeding diet (depending on species)

When it comes to feeding, robber flies have piercing and sucking mouthparts and a predatory diet, feeding on other insects, including bees, wasps, and spiders. Wasps have chewing mouthparts, and their diet can consist of other insects, nectar, or both, varying by species.

  Robber Flies Wasps
Wings 2 wings (fast and agile) 4 wings (greater lift capacity)
Eyes & Vision Large compound eyes (excellent vision) Large compound eyes (good vision)
Mouth & Feeding Piercing and sucking (predatory diet) Chewing mouthparts (diverse diet)

Behavior and Diet

Prey and Predation

Robber flies:

Wasps:

  • Predators of insects like caterpillars
  • Also eat nectar and pollen for sustenance

Mimicry and Defense

Robber flies and wasps have developed unique ways to protect themselves and hunt for prey.

Robber Flies

Wasps

  • Bright body colors
  • Warning markings
  • Stinging capability

Comparison Table

Feature Robber Flies Wasps
Prey Flying insects (e.g., spiders, grasshoppers) Insects, nectar, pollen
Hunting Technique Mid-air ambush Actively searching prey
Mimicry Bee and wasp mimics Warning colors and markings
Defense Mimicry, long legs, bearded face Stinging capability, warning colors

These predacious insects display fascinating adaptations in their behavior and diet, showcasing the diversity and complexity of their survival strategies.

Life Cycle and Reproduction

Eggs and Larvae

  • Robber Flies: Females lay eggs in soil or decaying wood1. The hatched larvae are predaceous, feeding on other insect larvae2.
  • Wasps: Female wasps lay eggs on or inside a host (e.g., spider egg sacs)3. The tiny wasp larvae feed on the host, such as spider eggs4.

Development and Adult Stages

  • Robber Flies:
    • Adult robber flies are medium to large in size5.
    • Their habitat includes pastures and sunny areas6.
    • They prey on flying insects, including other flies7.
  • Wasps:
    • Wasp mantidfly species are smaller than robber flies8.
    • They are commonly found in gardens, fields, and meadows9.
    • Adult wasps feed on nectar and are not predatory10.

Comparison Table:

  Robber Flies Wasps
Eggs Location Soil, decaying wood11 Host (spider egg sacs)12
Larval Diet Other insect larvae13 Host (spider eggs)14
Adult Size Medium to large15 Smaller than robber flies16
Habitat Pastures, sunny areas17 Gardens, fields, meadows18
Adult Diet Predaceous on flying insects19 Nectar, not predatory20

Ecological Role and Interaction

Beneficial Insects in the Garden

Robber flies and wasps serve essential roles in the garden by helping control various pest populations. They both act as predatory insects preying on garden pests like beetles, ants, and aphids.

For example, wasps, especially paper wasps, are known to feed on caterpillars and other insects harmful to plants. In contrast, other wasps like parasitic wasps lay their eggs on or in specific pest insects, benefiting the plants.

Similarly, robber flies are important predators of flying insects, including beetles and aphids. They also feed on various insect larvae that might damage plants in your garden.

Pest Control and Management

To efficiently use these beneficial insects for pest control, it’s essential to provide them with a supportive habitat. Encouraging the presence of robber flies and wasps starts with having a diverse garden, including flowering plants that attract them.

Some ways to create a favorable environment for beneficial insects include:

  • Planting a variety of flowering plants that provide pollen and nectar
  • Using non-toxic methods of pest control to avoid harming beneficial insects
  • Providing shelter and nesting sites for robber flies and wasps, such as deadwood or untreated wood piles

A comparison table of robber flies and wasps as beneficial insects in the garden:

Characteristic Robber Flies Wasps
Prey Flying insects Caterpillars, pests
Life Stage as Predator Adult Adult and larva
Nesting Habitats Soil, decaying wood Twig or tree cavities, plant stems, under eaves

By promoting a healthy and diverse garden environment and understanding their ecological roles, you can harness the pest control potential of beneficial insects like robber flies and wasps for a balanced and thriving ecosystem.

Identification and Observation

Physical Features and Characteristics

Robber Flies:

Wasps:

  • Wasps have a head, thorax, and abdomen, connected by a thin waist.
  • They have antennae and six legs.
  • Coloration varies but many are black, brown, or yellow.

Comparison Table:

Feature Robber Fly Wasp
Head Bearded and concave between eyes Standard insect head
Abdomen Long and tapering Segmented
Legs Long Short
Waist No Yes
Color Mimics bees/wasps, varies Varies
Scientific Order Diptera (Brachycera) Hymenoptera
Proboscis Present for piercing prey Absent

Where to Find and Observe

Robber Flies:

Wasps:

  • Common in gardens and woodlands.
  • Nest in trees, underground, or buildings.
  • Can be observed from spring to fall, but peak activity in late summer.

Example:
During July and August, you might see a robber fly perched on foliage, mimicking a wasp, while a nearby wasp might be flying around a nest in a tree.

Additional Resources

Photographic Guides and Image Galleries

For a better visual understanding of robber flies and wasps, consider exploring these resources:

Expert Organizations and Naturalists

For more in-depth information about robber flies and wasps, consult expert organizations and naturalists:

  • Entomological Societies: Groups like the Entomological Society of America offer knowledge about various insects, including robber flies and wasps. They often publish scientific studies and provide access to experts in the field.
  • Naturalist Blogs and Websites: Many passionate naturalists share their expertise and experiences with insects on blogs and websites. For example, naturalist Eric R. Eaton offers insights about many insects, including robber flies and wasps.

Comparison Table

Feature Robber Flies Wasps
Wings 2 wings 4 wings
Mouthparts Prominent beak-like proboscis Equipped with mandibles for biting or stinging
Body Appearance Hairy, long tapering abdomen Smooth, often with narrow waist
Living Habitats Open areas, often perching on plants Can be found in various habitats, nest in protected locations
Diet Predaceous on flying insects like leafhoppers and white grubs Omnivorous; feed on insects, larvae, and sometimes plant nectar

Key Differences

  • Robber flies have 2 wings, while wasps have 4 wings.
  • Robber flies have a prominent beak-like proboscis for feeding, while wasps have mandibles for biting or stinging.
  • Robber flies have a hairy body and long tapering abdomen, while wasps usually have a smooth body and narrow waist.
  • Robber flies are predaceous and feed on flying insects like leafhoppers and white grubs, while wasps can be omnivorous and feed on insects, larvae, and sometimes plant nectar.

Footnotes

  1. https://entomology.ces.ncsu.edu/biological-control-information-center/beneficial-predators/robber-fly/ 2 3 4 5 6 7 8
  2. https://texasinsects.tamu.edu/wasp-yellowjacket/ 2 3 4 5 6 7
  3. https://texasinsects.tamu.edu/robber-fly/ 2 3
  4. https://www.ncwildlife.org/Learning/Species/Inland-Fishes/Insects/Plan-to-Conserve-Bees-Wasps 2 3
  5. https://texasinsects.tamu.edu/robber-fly/
  6. https://education.mdc.mo.gov/discover-nature/field-guide/robber-flies
  7. https://education.mdc.mo.gov/discover-nature/field-guide/robber-flies
  8. https://entomology.umn.edu/wasp-mantidfly
  9. https://entomology.umn.edu/wasp-mantidfly
  10. https://entomology.umn.edu/wasp-mantidfly
  11. https://entomology.ces.ncsu.edu/biological-control-information-center/beneficial-predators/robber-fly/
  12. https://entomology.umn.edu/wasp-mantidfly
  13. https://entomology.ces.ncsu.edu/biological-control-information-center/beneficial-predators/robber-fly/
  14. https://entomology.umn.edu/wasp-mantidfly
  15. https://texasinsects.tamu.edu/robber-fly/
  16. https://entomology.umn.edu/wasp-mantidfly
  17. https://education.mdc.mo.gov/discover-nature/field-guide/robber-flies
  18. https://entomology.umn.edu/wasp-mantidfly
  19. https://education.mdc.mo.gov/discover-nature/field-guide/robber-flies
  20. https://entomology.umn.edu/wasp-mantidfly

 

 

 

 

 

 

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 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: Robber Flies

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10 Comments. Leave new

  • I saw a large insect today. looked kind of like a dragonfly and horsefly. huge eyes and big abdomen. it turned its head to watch me, then suddenly a bee flew in front of me and this thing flew up and grabed it “in flight”, right in front of my face. WOW ! II don’t like bees, but I’m glad it got the bee
    instead of me. I looked it up, and sure enough it was a robber fly. Awesome.

    Reply
  • I saw a large insect today. looked kind of like a dragonfly and horsefly. huge eyes and big abdomen. it turned its head to watch me, then suddenly a bee flew in front of me and this thing flew up and grabed it “in flight”, right in front of my face. WOW ! II don’t like bees, but I’m glad it got the bee
    instead of me. I looked it up, and sure enough it was a robber fly. Awesome.

    Reply
  • Even robber fly larvae are predatory and can be found in leaf litter and around fallen logs devouring grubs and similar creatures. They tend to hang out in my herb bed when my mint and oregano are blooming, because those blooms attract a huge number of flying insects.

    Reply
  • Teddy Alfrey
    June 30, 2016 4:45 am

    It was pretty small. I would say your 5mm is about right.
    Suddenly, they are all over my wife’s garden and seem to enjoy dining at the edge of day-lily petals.
    Also, once they have something to eat, they stay put long enough to line up a nice shot. I used a macro lens that required getting about two inches from the subject with a flash held six inches above, and got several shots. I’m wondering if its brain doesn’t have enough circuitry to flee and eat at the same time.

    Reply
  • Do these come into NE Alabama? Looks just like the “hopping bee-like” insect that intrigues and scared me last week.

    Reply
  • Andy Berryhill
    November 3, 2018 9:20 am

    I found one in Louisiana

    Reply
  • P. fulviventris seems to be more lookilike, but the northernmost distribution is Georgia.

    Reply

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