Looks to me like a Greater Mythical Invisible Moth caterpillar - although I might manage a better guess with a picture! 

Chris

Here’s an interesting fact on Garden Tiger moths for you!  Passively foraging bats emit regular pulses of high frequency (ultra)sound. These in turn echo back off the prey and give the bat an indication of the size, flight speed, flight direction and even species of potential prey detected. As the bat closes in this pulse rate increases significantly so that information on the exact location of the prey (and even an interception course) can be determined with ever increasing accuracy. This volley of terminal phase sound is called a feeding buzz and is very much akin to a wet fart on the auld bat detector; as me tutor used to say.

Interestingly many moth species have evolved to detect bat calls and will take evasive action when exposed to them (particularly the terminal feeding buzz). Typically such an action might include closing the wings and dropping like a stone from the air, thus avoiding any interception course identified by the bat. In response, some species of bat specialising in moth predation (Long-eared bats in the UK) have evolved relatively massive ears to enable them to hunt using direct prey generated sound (without the use of ultrasound), therefore overriding the moth’s inherent advantage. Now the Garden Tiger (Rhrooorrr) is a highly unpalatable/toxic species and at some point in time evolved to generate a clicking sound in response to a bat’s terminal feeding buzz (its garish colours advertise this to diurnal predators, however, this is not much use when outwitting sonar). Anyhow, there are two suggested reasons for this ingenious trick a) the clicks generated confuse/jam the bat’s echolocation system enabling the moth to escape b) it is an associative learning device designed to advertise its unpalatability. I have to say I think the latter more plausible, since young, inexperienced, Long-eared bats have been known to take Tiger moths but rarely the adults.

I love the evolutionary process of that, nature’s little beasts continually trying to overcome adversity. At the risk of sounding overly anthropomorphic, I think that makes the Garden Tiger moth a little bit special (but not in the simple minded sense of the word!)