The common green bottle fly (Lucilla sericata) is one of the most well known fly species seemingly found around the world, living on the detritus and excrement from animals and humans alike. I am no dipterist (an entomologist who studies flies), though there are more than you might imagine as they even have a dipterist society. I just find that macro photography of some of the small things in life make for interesting photography and this fly found in the lab ended up being the subject of a photographic study.
Here are the fly antennae and arista (sensory organs with hair bristles) at the front of the head in the depression between the compound eyes. The compound eyes while delivering poor resolution and limited distance vision, do cover a wide field of view permitting the fly to see in a greater than 180 degree arc. They likely also allow the fly microscopic vision. I actually would be very interested one of these days in reconstructing the entire visual system of an invertebrate like a fly with connectomics technologies that we are currently applying to the understanding of the mammalian visual system. The applications of a better understanding of the invertebrate visual system are pretty remarkable with benefits from everything from artificial vision to unmanned aerial vehicles (UAVs).
The top view of the fly head shows the articulation between the head and thorax along with the superior compound eyes and if you look closely, you’ll see the ocelli or simple eyes that are used in insects likely for flight orientation.
A closer view of the ocelli. Covering UAVs in ocelli like simple imaging systems seems like a good approach to solving many of the problems with UAVs including the limited field of view imposed by traditional camera systems as well as making them active components in optical cloaking technologies designed to make the UAV difficult to see.
The underside of the fly showing the spiracles in the abdomen which are essentially ports or holes that provide a means for insects to breathe through diffusion of air into the body cavities.
A closeup of the spiracles in the abdomen. Interestingly, these ports represent essentially a passive system of oxygenation as the air enters the ports and gets direct access to the tissues. They are however, more than passive structures as they can be actively opened or closed to limit water loss in dry climates or to limit water access to tissues in wet environments or even noxious chemical agents. It is thought that this passive respiratory system limits the size of insects, though it is not strictly a passive respiration. If this is correct, it may in fact explain some of the insects of the carboniferous period that reached truly intimidating sizes. Can you imagine a dragonfly with a 2.5ft wingspan?