Insect · GBIF taxon 1659610
Northeastern Hammertail
Efferia aestuansAlso known as Hammer-tailed Robber Fly, Northeastern Robber Fly
Northeastern hammertails are voracious aerial predators that perch on exposed twigs or sunlit ground to scan for flying insects. Females possess a distinctively flattened, hammer-shaped ovipositor used to tuck eggs securely into crevices and plant stems. Their muscular thorax and spiny legs allow them to ambush and snatch prey as large as bees, wasps, and beetles right out of midair.
PredatoryRobber FlyInsect
1 / 7—observations
—countries
—peak records
Least ConcernConservation statusIUCN Red List categoriesLCNTVUENCREWEXLeast ConcernRed List categories, explained →
Diet & prey
- Bees
- Wasps
- Flies
Predators
- Birds
- Spiders
- Lizards
ThreatsWidespread pesticide use and habitat disruption
HabitatsFields, meadows, forest edges, and sunny clearings
Life span1 to 2 years
Size / weightNot available
Classification
- OrderDiptera
- FamilyAsilidae
- GenusEfferia
- SpeciesEfferia aestuans
Range data is not available yet.
Interaction riskLow
- Low
- Moderate
- High
- Very high
- Why interaction risk is low
- Capable of delivering a sharp bite if handled; observe safely without touching.
- Why it is dangerous
- Injects digestive saliva through a sharp proboscis when squeezed, causing localized pain and burning sensations.
- How to recognize a risky encounter
- Look for prominent bulging eyes, a grey hairy face beard, and a silver-grey abdomen ending in a wide hammer shape.
- What to do
- Observe perching individuals quietly; do not attempt to catch them in bare hands.
Responsible observation
- Spotting Guide: Search exposed branches, garden fences, and bare patch ground in full sunlight.
- Approach Technique: Move slowly from behind to avoid triggering its rapid escape reflex.
Prey Species Andreas Trepte / CC BY-SA 2.5 · cc-by-sa
Prey Species no rights reserved, uploaded by Richard Fuller · cc0
Robber Fly Relative (c) Judy Gallagher, some rights reserved (CC BY-SA), uploaded by Judy Gallagher · cc-by-sa
Help improve the field guideSomething wrong?
Checking your Fauna account…Report a name, category, or profile issue for review.