Fauna
Insect

Spot-tailed Lion Fly

Promachus vertebratus

Also known as Lion Fly, Giant Robber Fly

Spot-tailed lion flies are formidable aerial predators known for ambushing wasps, bees, and beetles directly mid-flight. They perch on high grass stalks or sunlit leaves, watching for prey with exceptional vision before launching a sudden strike. Their thick golden-grey pile and distinctly banded abdomen help them blend into sun-dappled prairie edge habitats across North America.

PredatoryInsectSun-Loving
Spot-tailed Lion Fly reference1 / 5
(c) psweet, some rights reserved (CC BY-SA), uploaded by psweet · cc-by-sa
—observations
—countries
—peak records
Not EvaluatedConservation statusIUCN Red List categoriesLCNTVUENCREWEXNot Evaluated — not placed on the risk ladderRed List categories, explained →
Key facts
Diet & preyHoney bees, Paper wasps, Beetles
Predators
  • Insectivorous birds
  • Orb-weaver spiders
  • Praying mantises
ThreatsPesticide use, habitat fragmentation
HabitatsFields, prairies, meadow edges, open woodlands
Life span1–2 years (total lifespan including soil larva)
Classification
  1. FamilyAsilidae
  2. SpeciesPromachus vertebratus
Range & activity
Range data is not available yet.
Safe observation
Interaction riskLow
  1. Low
  2. Moderate
  3. High
  4. Very high
Why interaction risk is low
Capable of delivering a painful bite if handled directly; observe from a safe distance.
Why it is dangerous
Uses a strong proboscis to inject paralyzing digestive fluids into prey, causing a sharp bite if pressed against human skin.
How to recognize a risky encounter
Look for a large grey and gold robber fly with a stout pointed beak perching on top of vegetation.
What to do
Do not squeeze or corner perching insects; view them calmly without physical contact.
Responsible observation
  • Observation: Approach slowly on sunny mornings when flies perch atop tall weeds to warm up.
  • Photography: Position your camera at eye level with their perch without blocking direct sunlight.
  • Handling: Avoid grabbing with bare hands to prevent defensive bites from their sharp beak.
Related species
Help improve the field guideSomething wrong?

Report a name, category, or profile issue for review.

Checking your Fauna account…