The Longbanded Silverline (Spindasis lohita), Family Lycaenidae, is a beautiful insect with a remarkable structure – a tail, or ‘false head’ – at the end of its hind wing. There is a bright orange tornal patch – the tornus is the posterior corner of the butterfly wing – on both sides of the wing. There is also a black eye-spot and two pairs of white-tipped, filament-like black tails, or ‘false antennae’, at the end of the wing. Interestingly, many lycaenids have similar black and orange eye-spots and single or double tails. For example, the Common Tit (Hypolycaena erylus himavantus) also has white-tipped, double tails similar to this species (1). So presumably it was a feature that evolved at sometime during the history of this family. Black and orange make a very eye-catching colour combination.
It is widely assumed that these structures are a ‘false head’ (or ‘fake head’), which acts to divert predatory attacks, e.g. bird pecks, away from the real head (and body) and towards the back of the butterfly. There is plenty of evidence that butterflies really do get pecked at, or on, these hindmost eye-spots (2). It is surprising therefore, that very little rigorous experimentation has been carried out to thoroughly investigate this phenomenon. In other words, the ‘false head’ hypothesis has not been tested scientifically. That is not to say it is not true, it is just a subject that ‘remains ripe for testing’ according to Professor Martin Stevens (3).
The fact that these butterflies invest so much time and energy into producing these deceptive structures and moving the little tails about like false antennae, is to my mind, quite convincing circumstantial evidence for their utility in avoiding predation, or surviving an attack. It is clear how prominent the ‘false head’ is – and might appear to a bird – when looking down on the butterfly from above (see photo below) like a bird might see it. The real head is partly hidden underneath the wings, but the ‘false head’ is very prominent.
The lovely wing colours of this butterfly are a tapestry, to borrow a term used by lepidopterists, of tiny overlapping scales of different colours: red, silver, orange, white and black. The scales can be seen in two excellent close-up photographs of the wings of this butterfly on this webpage (4). Males of this species also have bright, iridescent blue patches on both dorsal fore- and hind-wings. It is possible that these, together with the contrasting orange patches, could also act to startle and deter a predator and give the butterfly time to make its escape.
- Stevens, M. (2016). Cheats and Deceits: How Animals and Plants Exploit and Mislead. Oxford University Press.
I am a retired entomologist with a background in quarantine pests and invasive invertebrates. I studied zoology at Imperial College (University of London) and did a PhD on the population dynamics of a cereal aphid (Metopolophium dirhodum) in the UK. I spent 5 years with the British Antarctic Survey studing cold hardiness of Antarctic invertebates and 17 years with the Food and Environment Research Agency. My main interests now are natural history, photography, painting and bird watching.