Name: _________________________
Date: __________________________
The Grasshopper: External and Internal Anatomy
Introduction:
Grasshopper morphology is relatively unspecialized as they are not greatly differentiated
from the appearance of ancient insect groups. In fact, entomologists have found it useful to fully
understand grasshopper morphology before studying groups that are more highly modified. The
Eastern lubber grasshopper, Romalea guttata is a large, slow-moving herbivore that has reduced
wings and can barely fly. They are found in the southeastern U.S. and their exceptional size and
ease of capture make them favorites for dissection.
Because of their relatively small size and difficult to distinguish internal anatomy, we
will be focusing on the external anatomy of the grasshopper for this dissection. In order to
complete the dissection, you will need to refer to the labeled diagram below and any other
diagrams you can locate in the text materials provided. Also, be sure to answer the questions
listed throughout this lab.
The numbered structures are referred to in bold-faced type in the descriptions below.
1. head
2. thorax
3. abdomen
4. antenna
5. ocellus
6. compound eye
7. hindwing
8. tympanum
9. forewing
10. jumping leg
11. ovipositor
12. spiracle
13. segment
14. walking leg
15. coxa
16. trochanter
17. femur
18. tibia
19. tarsus
20. maxilla
21. mandible
Dissection:
1. Get a lubber grasshopper from your instructor. Wash the grasshopper off under the sink and
put in a pan.
2. Examine the external anatomy of the grasshopper. Distinguish between the head, thorax,
and abdomen. Then look at the wings. The front wings are thickened into a tegmen and
function to protect the membranous hind wings. Note how the wings are attached so that
they can pivot and fold over the back.
Question #1
How might the adaptation of wings that fold backwards be explained from an
evolutionary perspective? In other words, what might be the advantage of having wings
that fold?
Remove the wings so you can continue dissection.
3. Next examine the head, which is composed of several fused plates called sclerites including
the frons, clypeus, and gena that compose the head capsule. Locate the ocellus (simple eye),
compound eye, and antenna.
4. Look at the mouthparts. Use a probe and handlens to examine the mouthparts including the
labrum, mandibles, maxillae, and labium.
Question #2
What is the function of these parts?
5. Cut open the tough head capsule and look for the brain and examine the internal support
structures.
6. Remove a leg and identify the segments: coxa, trochanter, femur, tibia, and tarsus.
7. Locate the thoracic spiracles, which are the openings to the tracheal system.
Question #3
What is the function of the tracheal system?
8. Look at the abdomen and locate the abdominal spiracles.
8. Place the grasshopper right side up and carefully cut through the exoskeleton with your
scissors. Place some water in your dissecting tray, which will help float the organs,
particularly the trachea which will look like a mass of branched silvery tubes. If you are
careful you will see the heart, which is a dorsal tube, often it gets removed with the
exoskeleton. Notice the many muscles that are attached to the exoskeleton, try to follow
some and discern their purpose.
Question #4
Describe the location and proposed purpose of one of the muscles you located.
9. Locate the digestive system. If your grasshopper is female everything may be covered with a
large yellow mass of ovaries, follow them back to the ovipositor. Then push the ovaries
aside and look for the gut. The esophagus leads from the mouth to the crop which functions
to store food. Under the esophagus you may be able to see very small grayish grape-like
clusters of the salivary glands. This leads to the gizzard and to the stomach. Just posterior to
the gizzard, find the fingerlike projections called the gastric caeca. They are attached at the
junction between the gizzard and the stomach. Follow the gut back to the hindgut where the
very slender malpighian tubules, are attached. These act as a kind of kidney for removing
nitrogenous wastes in insects.
Question #5
Which is larger, the gizzard or the stomach?
Question #6
In which one do you think food remains the longest? Why do you think this?
10. Remove the digestive system and look for the ventral nerve chord and the ganglia this will
appear as two white lines along the inside of the sternum which are periodically connected
with larger white masses.
Question #7
Which characteristics make the grasshopper well adapted for its life on dry land?