I know! I too go all shivery looking at this fly. I'd rather not, but he happened to sit still long enough for me to take a close up, so we might as well. Knowledge is power and all that.
To start with, yes he is a common greenbottle (as opposed to bluebottle), and he is unfortunately a blowfly. Which is a bit worrying because they lay their eggs on dead things. I'm concerned that Garden 65 is littered with the poor little bodies of dead mice and birds. I hope not.
On the plus side he has an interesting binomial name: Lucilia ceasar, which means Shining Ceasar. This name was given by Carl Linaeus, the founder of the modern taxonomy system. I wonder what it was about this nasty fly that reminded Carl of imperialist Rome.
Here's the science bit:
you notice his thorax (the top bit that we can see is called a scutum) has lots of bristles (setae) on it? Well, apparently that patterning of those bristles is how those who take an interest in flies (diptera) manage to distinguish one species from another. Now I've gone cross-eyed trying to find the definitive explanation of our fly's bristles (I mean, setae) but can't find it, so I shall report back on what I've found so far.
That first deep groove behind the head and before the wings is called the transverse suture. There are many names for the position of the bristles (ah! setae) but lets keep it simple and say our fly has lots of postsutural dorsocentral setae.
I'm sure you'll be able to impress someone with that observation next time you see a shiny fly.
