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:
- Wasps:
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:
- Predators of flying insects, such as spiders and grasshoppers
- Catch prey mid-air
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
- Bee and wasp mimics
- Long legs and distinctive bearded face
- Humpbacked appearance
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:
- Wasps:
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:
- Robber flies have a distinctive bearded face and concavity between the eyes.
- They often have long legs and a long, tapering abdomen.
- Some species mimic bees and wasps.
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:
- Associated with soil or decaying wood.
- Larvae prey on other insect larvae.
- Active in July and August, especially in places like Iowa.
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:
- BugGuide: An extensive online photographic guide covering North American insects, including robber flies and wasps. You can find images, taxonomy, and general information about each insect family.
- Extension Office websites: Several university extension offices provide detailed photographic guides to insects commonly found in their regions, such as North Carolina State University’s gallery of robber flies.
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
- https://entomology.ces.ncsu.edu/biological-control-information-center/beneficial-predators/robber-fly/ ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7 ↩8
- https://texasinsects.tamu.edu/wasp-yellowjacket/ ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7
- https://texasinsects.tamu.edu/robber-fly/ ↩ ↩2 ↩3
- https://www.ncwildlife.org/Learning/Species/Inland-Fishes/Insects/Plan-to-Conserve-Bees-Wasps ↩ ↩2 ↩3
- https://texasinsects.tamu.edu/robber-fly/ ↩
- https://education.mdc.mo.gov/discover-nature/field-guide/robber-flies ↩
- https://education.mdc.mo.gov/discover-nature/field-guide/robber-flies ↩
- https://entomology.umn.edu/wasp-mantidfly ↩
- https://entomology.umn.edu/wasp-mantidfly ↩
- https://entomology.umn.edu/wasp-mantidfly ↩
- https://entomology.ces.ncsu.edu/biological-control-information-center/beneficial-predators/robber-fly/ ↩
- https://entomology.umn.edu/wasp-mantidfly ↩
- https://entomology.ces.ncsu.edu/biological-control-information-center/beneficial-predators/robber-fly/ ↩
- https://entomology.umn.edu/wasp-mantidfly ↩
- https://texasinsects.tamu.edu/robber-fly/ ↩
- https://entomology.umn.edu/wasp-mantidfly ↩
- https://education.mdc.mo.gov/discover-nature/field-guide/robber-flies ↩
- https://entomology.umn.edu/wasp-mantidfly ↩
- https://education.mdc.mo.gov/discover-nature/field-guide/robber-flies ↩
- https://entomology.umn.edu/wasp-mantidfly ↩
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.
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.
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.
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.
Your image is quite detailed and beautiful.
Do these come into NE Alabama? Looks just like the “hopping bee-like” insect that intrigues and scared me last week.
Yes there are numerous species of Robber Flies in Alabama.
I found one in Louisiana
P. fulviventris seems to be more lookilike, but the northernmost distribution is Georgia.
Thanks Cesar. Here is a link to a BugGuide image.