Adult - Head

In anterior view, the head is dominated by two large compound eyes, purple-brown in color, which occupy each side of the head. The surface of each eye is divided into about 4,000 facets, each an irregular hexagonal shape. Each facet is a visual unit so that the fly perceives a mosaic of a scene.

At the top of the head (vertex), between the compound eyes, are three simple eyes (ocelli), arranged in a triangle. Lower on the head between the eyes is the one pair of antennae partially set in a depression.

The area above the bases of the antennae and below the ocelli is very narrow in male flies and relatively wide in females. Therefore, in males the compound eyes appear to be set close together (holoptic) while in females they appear to be set far apart (dichoptic).