Anatomy of a flower fly.

Yuck! That is the reaction many people give when they see one of my macro images; photographs of invertebrates turned to giant putrescent slime creatures that nightmares are made of. Consider for a moment the wonder of their lineage. Insects alone account for 80% of all Animalia. That kind of diversity tells us that they have been phenomenally successful on this planet. The design, although repulsive to some, has allowed success on an unprecedented scale. You have to admire their achievements, if not their anatomy.

Have a close look at a few of the amazing adaptations of the flower fly. You can see the labellum, one of the mouth-parts, jutting out beneath the fly's head (most of it is covered by the flower's pistol). Food channels in the lower part of this structure allow liquids to move upwards through capillary action. All the fly has to do is touch a wet surface and nutrients are immediately taken up. The antenna and arista (part of the antennae in flies) are well adapted to sensing aspects of the environment not immediately available to us. Depending on the species it can detect moisture, heat, wind movements, hearing, and possibly other environmental phenomena. The maxillary palps contain sensory cells capable of detecting smells and tastes.

The eyes of an insect are well suited to detect light-change, colour, and motion. Simple eyes are well suited to detect light change which is why your shadow can cause a housefly to scatter before its life is shortened. The compound eyes detect colours well in the blue and green spectrum but usually poorly in the red and yellow frequencies. Ultraviolet light also seems to be detectable, at least in the lower wavelengths. Many flies also exhibit the ability to detect polarized light which is useful in navigation. Compound eyes are especially good at detecting movement, which is why trying to catch one is so difficult.

One of the greatest abilities shown by insects is their ability to fly. This trait alone accounts for a lot of their success. Flies are unusual in the insect world in that they have only one pair of wings, not two. The second set of wings has been adapted into a pair of halteres. You can see it on the fruit fly photo just above the femur of the last leg and below the wing. It is thought the halteres act as balancing organs to assist in flying. You can see an excellent slow-motion video here.

Although initially disgusting to some, flies (all invertebrates actually) are remarkable creatures. Next time you eat crab or lobster spend a moment appreciating how wonderful their design is. It's really rather marvelous.

Thanks for reading.     Ericspix     Eric Svendsen