Hammerhead Worm (often specifically the Broadhead Planarian)
Scientific Name: Bipalium spp. (likely Bipalium kewense or Bipalium adventitium)
Order & Family: Order: Tricladida; Family: Geoplanidae
Size: Varies by species, but Bipalium kewense can grow quite large, commonly 20 to 30 cm (8 to 12 inches) in length, though smaller specimens are often seen.
Natural Habitat
They thrive in dark, cool, and moist environments. Commonly found in gardens, under rocks, logs, leaf litter, and sometimes in greenhouses. They are an invasive species found across parts of the United States, Europe, and Asia.
Diet & Feeding
Carnivorous and predatory. They primarily feed on earthworms, slugs, insect larvae, and sometimes other hammerhead worms. They secrete enzymes to dissolve their prey before consuming it.
Behavior Patterns
Nocturnal and sensitive to light and dehydration. They track prey using slime trails. A notable feature is their ability to reproduce asexually through fragmentation; if cut into pieces, each piece can often regenerate into a new worm.
Risks & Benefits
Risks: They secrete a neurotoxin called tetrodotoxin (similar to pufferfish), which can cause skin irritation in humans and is dangerous if ingested by pets. Ecologically, they pose a threat to beneficial earthworm populations. Benefits: None significant in non-native environments.
Identified on: 3/7/2026