On the Cutting Edge: Grasshopper Dissection
Grasshoppers are excellent specimens for invertebrate anatomy studies. The Louisiana lubber grasshopper (Romalea) is most often studied since it is large and readily available. A careful investigation of this specimen should lead students to a better understanding of grasshopper behavior and how well the grasshopper’s anatomical structures are adapted to its habitat. This activity is designed for students in grade 9 through college and can be adapted for use in middle school classes.
- Carolina’s Perfect Solution® Grasshoppers
- Dissecting pan with wax or vinyl pads
- Dissecting pins
- Hand lenses
- Observe the grasshopper’s external anatomy. Members of class Insecta have 3 main body regions: the head, thorax, and abdomen. Locate each region on the grasshopper using the drawing below as a reference.
- The grasshopper’s thorax has 3 segments, each of which bears a pair of legs. The 2 posterior thoracic segments each have a pair of wings, also. Study the grasshopper’s thorax and locate the 3 segments and their appendages.
- Observe the abdomen. Find the spiracles, the tiny openings into the tracheae. Tracheae are a system of tubes that function in gas exchange. These “breathing tubes” extend through much of the body. Spiracles can also be seen in the thorax.
- The grasshopper’s head possesses sensory structures. Observe the 2 compound eyes and the 3 simple eyes (ocelli) located between them. The simple eyes do not form images but do sense light. One pair of antennae can also be seen.
- Observe the mouth and feeding appendages. The mouth contains a pair of mandibles and 2 pairs of maxillae.
- Place the specimen in the dissecting pan ventral side up. Use scissors to cut through the exoskeleton’s ventral side from the head to the posterior end of the abdomen.
- Pull the cut sides apart and observe the tracheal tubes running into the internal organs. Pin each side of the insect to the dissecting pan.
- Locate the yellow fatty tissue that covers the internal organs. Carefully remove this layer with forceps to observe the organs. Refer to the drawing below to locate the structures discussed in the following steps.
- Locate the digestive system. The crop, found at the anterior portion of the digestive tract, is an organ for storing food. The gastric cecae, or digestive glands, are attached to the stomach.
- Identify the reproductive organs that lie on either side of the abdominal digestive organs. In a female, the ovary appears as a series of tubules containing rodlike eggs. Females also have ovipositors, 4 curved projections at the end of the abdomen. These are used to dig a hole for egg deposition. In males, the testis is a coiled cord containing many tubules. The posterior end of the male abdomen has claspers, which are used during reproduction.
- After you have completed the dissection, dispose of the specimen in accordance with local guidelines and your teacher’s instructions.