18 Insect Anatomy – The Abdomen

Abdomen

The abdomen includes all of the body segments after the metathorax.

There are no jointed appendages (legs) or wings attached to the abdomen.

Just above and behind the hind leg of the grasshopper is the tympanum. It consists of a membrane stretched across an opening, which detects vibrations. Grasshoppers use sound in courtship, and territorial displays. The tympanum acts as an “ear” to detect those frequencies.

The tympanum will have different sizes, shapes, and locations in different insects.

Along the sides of the abdomen, just above the sutures between the tergites and the sternites, you will see one tiny hole per segment. These are the spiracles, or openings of the respiratory system.

You may also be able to see some spiracles on the thorax of some insects.

At the tip of the abdomen, there are two small “flaps”, called cerci. The function, shape, and size of the cerci vary considerably in different insects.

Here are photos of the genitalia of both sexes of grasshoppers, on the last abdominal segment. Which sex do you think is which? [The male grasshopper is on the left, and the female is on the right.]

The aedeagus (mostly internal) is used to transfer sperm to the female à the ovipositor, literally the “egg positioner”, is used to bury the eggs in hard-packed soil (in grasshoppers).

Both male and female genitalia can look quite different in various insects. They are often important for identifying insects to species.