The abdomen houses the stomach and reproductive organs. The abdomens of arthropods usually appear to be made up of separate segments or rings. All arthropods have segmented bodies, though the segments may be impossible to see because in some arthropods they have grown together. For example,most spiders' abdomens do not appear to have segments, even though their internal anatomy shows segmentation. Only an adult insect can have wings, but not all adult insects will have wings.
Flies have only one pair of wings.
The wings are always on the thorax, the same body part that has the legs. In some, the mouthparts are not visible because they have been pulled back into the head. Springtails and fly larvae are good examples of this. Other fly larvae have mouthparts that look like a pair of hooks. Spiders and centipedes have fangs for injecting poison into their prey.