I finally read Twilight, and after hours of internet research, I’ve found a solution to a major problem I had with the story. I know why the vampire sparkles!
Of course, innate body glitter is just the latest thing wrong with vampires at large, so I’ll start with the broader picture and work my way to the answer to that new riddle.
First, I assert that vampires must be giant, highly evolved insects. That makes sense because most of the hematophages in the natural world are bugs.
Second, like many real bloodsuckers, vampires must feed before they reproduce. However, unlike anything in the natural world, vampires seem to reproduce entirely through horizontal gene transfer. If they don’t kill their victim outright, then vampire genes invade the host and trigger…
Metamorphosis. According to Twilight, the process takes days and is excruciatingly painful, which is logical given that the victim undergoes complete hystolysis and histogenesis without the benefit of a pupal stage, let alone general anesthesia.
But wait! How do vampires retain the memories of their human lives? Well, butterflies are apparently able to remember things they learned as caterpillars. While it’s doubtful that the same processes would apply identically to higher-order animals, anything is apparently possible with enough suspension of disbelief.
Furthermore, vampires appear to be ectothermic, or never warmer than their environment. ‘Cold-blooded’, in other words. Their stone-like ‘skin’ also seems more like an exoskeleton than warm, soft, human tissue.
What about vampires’ superhuman abilities? The Tiger Beetle is technically ‘the fastest running land animal’. The strongest animal is the world is the horned dung beetle. Insects also have incredible vision; most see colors invisible to humans and bees see in color at five times the speed we’re able. Vampires and other insects don’t breathe like we do, nor do they possess a human heartbeat. As an added bonus, invertebrates are notoriously hard to kill.
By now, I’m sure you’re all with me; vampires are bugs. But what kind? It took me a while to figure it out, but now I’m convinced that vampires are nothing more than overgrown, parasitic…
Butterflies!
There you have it. Vampires are gorgeous, metamorphosis is a key part of their development, and they are natural experts at camouflage and mimicry. Some butterflies have even been observed feeding on blood.
Why do they sparkle? That’s easy: Vampires, like butterflies, are covered in tiny iridescent scales.
Very... interesting... 
