What's That Bug? does not endorse extermination

I saw this critter in Hawaiian Paradise Park on the east side of the Big Island (Hawai’i) south of Hilo. I first saw a larger one that was gray-bodied and it had the same fan-shaped head. At first I thought it was a kind of earthworm or other kind of worm. But when I photographed this 2.5 in. one with the yellowish body and dark dorsal line, I noticed what appeared to be a slime trail. The larger gray one was about 6-7 in. long with a uniform thin body (not segmented like an earthworm), perhaps a bit thinner in aspect ratio that his one. It seemed to move faster than the typical slugs in Hawaii (Veronicella cubensis?) but perhaps it was the more animated movement of the fan-shaped head that created that illusion. The points of the head articulated like a slug’s "antennae". I didn’t want to turn it over to examine the ventral side. Might this be a juvenile form? Any idea what it is?
Les Chibana
Volcano, HI

Hi Les,
Thanks for sending this unusually colored Arrowhead Flatworm, a Planarium.

Update (04/26/2006): Arrowhead Flatworm in Maui
Aloha, I am impressed with the photo you just put up on your home page from the Big Island. We found this Arrowhead Flatworm in our outdoor shower a month ago, just after several days of rain. It was 4″ long and yellowish with black stripes down the entire length of it’s body. We had never seen one before so I contacted our local Dept. of Ag to inquire if it is considered an invasive species. Apparently the answer depends on your point of view. If you want earthworms for your garden, then the flatworm is invasive. If you have an abundance of the Giant African Snail, then you may appreciate the flatworm as it is a predator of said snail. I read on the internet that the flatworm expands to over twice it’s size after eating, but I have yet to find an earthworm to feed to it. It would not touch my composting worms. Keep up the excellent and entertaining work on your website! It is much appreciated. Aloha,
Kihei, HI

What's That Bug? does not endorse extermination

6 Responses to Arrowhead Flatworm

  1. lizacoyote says:

    i found these a lot in Texas are they wide spread?

  2. Paula says:

    Just found one of the brown worms in Alabama, Looks to be about 10 inches long. First one I have ever seen. Should I be contacting my Ag. Agent?

  3. Amy says:

    Hello, just found one of these last night on my porch. Took several pics of it.I was curious to what he was. Should I be contacting my local Ag. Agent?

  4. Charbum says:

    I see these in my backyard all the time I want to know if they are a widespread species

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