If the second picture is taken where this animal lives I am sure it is a terrestrial triclad (Platyhelminthes, Tricladida, Terricola). Are this pictures of the same animal?

Thank you, Ernest. These are different species - the first from southern India, second - from New Guinea, third from Sout-West Australia. These flatworms are so terrestrial, that afraid of water: In Peru I saw them running from raising river after rain.

As its systematic position is clarified, the animal goes away.

Congratulations to Ernest, he was fast!

My identifications (from third to first):

Third one: it is flat, obviously land planarian (Tricladida). Our Australian friends could probably identify it, although all identifications of these worms without a detailed histological study are only provisional.

Second one: Not as flat as the third one. I would like to see the head (are the eyes visible?), and I would to know if there is a proboscis. It looks like certain triclads but it resembles the land nemertean Geonemertes pelaensis.

First one: Also looks like a land nemertean, or a triclad... we need to see the same details.

As a general comment, I suggest that all requests for identifications should be provided with details about the geographic origin. That helps!

I just came about this question, Jean-Lou. I am not that fast (anymore LOL). Our Japanese friends (for the Indian species) and or Brasilian colleagues may help with the S. American species. Nikita: next time you take a picture to see the colours and put the animal in hot Bouin's fluid (or other fixative) and send it to a specialist if you really want to know the name. Keep in mind that it takes some work and time to make a proper identification.

If the discussion continues, the animal returnes. I tried to take it by pincer, but it was broken to three parts, two of which are running back separately. I could not find eyes and mouth on frontal end of any of them. Now they are all in alcohol (I had no hot Boui'n fluid in my tent). I study insects, and my interest to these animals is poordy diletantic-educative.

I am not surprised you did not find a mouth at the frontal end: it is mid-way! As you may know, triclads (like "Planaria") have a high regeneration capacity and some species even reproduce by fission. Also, when disturbed they fall in peaces. When you try to google "Tricalida" and/or "Geoplanidae" you'll find a lot information about these animals. They are heavy predators (may eat you insects!) and are used as indicators in ecology. Your question demonstrate once more that free-living flatworms (the so-called Turbellaria, now recognised as a paraphyletic grouping) are poorly known and their importance underestimated.

I agree with Jean-Lou. The second one is a nemertean, and the two others possibly land planarians. More deetails are required.

The second one is from New Guinea (Cyclop mountains)

Strongly suspect that the second photo from the Cyclops Mountains is Geonemertes pelaensis. The species occurs in New Guinea and other islands in the Pacific and Indian Oceans, and in the West Indies.

The species from India in the first photo could be Dolichoplana sp. but details (eyes) would be needed of the anterior end that might in any case be regenerating.

The species in the last photo from south-Western Australia is probably a new species in the Tribe Caenoplaninini.

If these animals represent taxonomic interest, I have them in alcohol.

One more species, from Chile

Agree that middle photo at start is probably Geonemertes.

Nice to meet old friends in this discussion ;-). Glad that the true specialists give their opinion now...