This morning on the porch floor I found a large caterpillar (6x1.5 cm), green with thin black lines that I cannot identify.
Can you help me?
CLOSED: Big caterpillar
Possibly Acherontia atropos (deaths head moth) - https://en.m.wikipedia.org/wiki/File:Acherontia_atropos_01.jpg
Thanks for your answer!
I must tell you, though, that despite the extreme variability of this larva I had read about is here
I find all the images quite unlike "my" both for the color, which is substantially dark green with only that kind of yellow "horn" and for the appearance. It has also moved and never "opened" like the examples I have seen in the sites mentioned above which, moreover, do not seem to have the hairs of which "my" specimen is provided and did not walk but moved "unraveling" .
Perhaps it is my ignorance that creates these doubts?
I do not claim to be 100% certain, but Acherontia atropos still appears to be the most likely suspect. I do not know of any other Italian sphingid caterpillars that have both the very knobbly 'horn' at the end of the abdomen, and the vertical black stripes on the head capsule. The 'hair' you see on your specimen is an artifact; not part of the caterpillar itself. It also is possible that your specimen either is diseased or is getting ready to pupate; both of these circumstances can affect the color.
I'm still mulling over this big caterpillar !!!! Did you notice the black spot on its abdomen? It looks like a wound. I got the idea that it could have been parasitized. What do you think about it?
Yes, I'd noticed the spot. That was my reason for mentioning that it might be diseased (which includes being parasitized).