A little secret about Berliners: They don’t tend to make use of their abundant lakes unless the weather forecast is predicting long hours of scorching sun. And since there hasn’t been much of that this summer, the beaches and waterfront lawns have had relatively few visitors. 

But my blood is too British for the prospect of an afternoon spent on the grass beneath an overcast and slightly weepy sky to be in any way off-putting. So last weekend, my family and I packed our swimming things and a picnic, and headed off to the breezy lake.  

Since it was "only" 20 degrees, we were alone but for the resident wildlife. Ducks, which I love. Mosquitoes, which I don’t, and would never try to save according to the ways of my zen colleague. And something I had never seen before.

It was brought to my attention by my daughter first shaking her wet swimming costume at the ground and then trying to scrape something off it with a stick. That something was a snake. A little snake. A very little snake. Okay, it was a caterpillar. But it was a big one. Honest. And once we finally managed to separate it from the bathing suit, which given its tenacious, sticky grip took a while, it writhed, flipped and raised its horned head.

Oh yes, you read right. It had a horn. A brilliant flash of luminous turquoise that looked like one of those things you really want to touch, but probably shouldn’t if you are at all partial to the concept of life. So, hands firmly behind our backs, we stood and watched, transfixed. We didn't scream much, and only quivered a little.

But what is it?

When the boat rental man walked past, not having a rush on customers and all that, I asked him if he could shed any light on the mysterious creature rearing up at our feet. He gave it the once over, shook his head and went to fetch the lifeguard, who since we were no longer in the water, had no lives to guard.

He strutted from his pier to where we were keeping a pathetic distance from the writhing creepy crawly, cast his eye over it, looked at us like we were the biggest numpties on the planet and said: "It’s a lime hawk caterpillar." Oh, right.

I nodded, clearly betraying the fact that I had no idea what he was talking about, because as he walked back to his chair overlooking the serenely empty lake, he said: "It’ll be a butterfly soon."

So now I know. Except strictly speaking, it will be a moth. A lime hawkmoth, which is also known by the more poetic and less military sounding name of Mima tiliae, feeds off lime trees not only on the shore of a deserted Berlin lake, but right across the Palearctic region.  

That being so, chances are I’ll come across another one in the future. And when I do, I will be all the wiser. I’ll know, for starters, that its turquoise blue horn, which by the way is not poisonous, is actually on its bottom as opposed to its head, which makes it more of a tail than anything else.  

And I’ll know too, that when it rears its head, it is in self-defense. So I won’t stand gawping at its fear. Nor will I shrink back at its size. I’ll be altogether tougher. After all, I’m not afraid to picnic in the rain.