Why do vampires sparkle?

Some time last year I was kind of obsessed with vampires.

I know, I know, not surprising. The whole world was.

I had grown up thinking that vampires shrivel and burn in the sunlight, probably thanks to early exposure to 'Interview with the Vampire' and 'Dracula'. To me, the vampires in 'Let the Right One In' (which they've remade, btw. Here's the trailer: surprisingly doesn't look bad like most American remakes do)made the most sense, what happened to them in sunlight was pretty gnarly. Second would be 'True Blood', stuff happens to them too under the sun. 'Twilight' however, didn't make any sense. So vampires sparkle in the sun, but nothing happens to them? What? Why? I always felt like I was missing something there.

Today I wandered upon this and sparkles made a lot more sense.

It makes the claim that a vampire is a highly evolved bug. Most of the world's blood suckers (referred to as hematophages in the post) are bugs. Vampires must feed before they reproduce, like fleas. To reproduce, they undergo horizontal gene transfer like some parasites which means that if they don't kill their prey, then the parasitic genes will be passed on into the host and will embed itself into the DNA and mutate the host.

The transformation into vampire is like the metamorphosis of a butterfly, but without the pupil stage. They then remember their lives as humans, just like butterflies can remember lessons from back in the caterpillar stage. They also have exoskeleton-like skin and are cold blooded. Vampires are faster, stronger, and have better vision, akin to the tiger beetle (fastest land animal), horned dung beetle (strongest animal), & most insects see better than humans (bees apparently process color 5x faster than humans). Also insects don't have heart beats and are super hard to kill!

and like butterflies, some of which feed on blood, they have tiny iridescent scales that shimmer in the sun! Also butterflies are highly adapted at camouflaging! Just like vampies that pretend they are normal high school students (even though they all look about 25)

More interesting is that if you read the comments, one person mentions that Guillermo del Toro's 1993 film Cronos is a vampire movie, and the parasite which turns the character into a vampire is a bug! I really want to watch this now. But tonight I'm going to watch Fallen Angels. I have 600 movies in my queue. Strange word. Q would be fine, so would qu, so would que, they all would be pronounced the same, so why the extra letters?