Grasshopper Dissection
Introduction
Insects are arthropods with jointed appendages, segmented bodies, and an exoskeleton composed of chitin. Insects are in the class Insecta, & are the largest and most diverse group of animals on earth. The genus Romalea is a large grasshopper common in the southeastern United States. Insects have three body regions (head, thorax, & abdomen), 3 pairs of legs attached to the thorax, a single pair of antenna attached to the head, mouthparts adapted for chewing or sucking, and two pairs of wings. Some insects may have a single pair of wings or be wingless. Insect legs are often adapted for digging, crawling, jumping, or swimming. The insects are mostly terrestrial; they breathe air which enters small lateral openings on the body called spiracles and circulates in a system of ducts to all organs and tissues. Their chewing or sucking mouth parts are adapted for feeding on plant or animal materials.
Classification:
Kingdom - Animalia
Phylum - Arthropoda
Class - Insecta
Order – Orthoptera
Objective:
Identify & label the internal & external anatomy of a grasshopper.
Procedure A: External Anatomy:
1. Obtain a preserved grasshopper & rinse off any preservative with water. Place grasshopper in
the dissecting pan.
2. Observe that the body of the grasshopper is divided into 3 regions --- the head, the thorax,
and abdomen. Label these on Figure 1 of your answer sheet.
3. Observe the parts of the head. Locate the large compound eyes on either side of the head and
the ocelli or three simple eyes. The ocelli are arranged in a triangle on the front of the head.
Both simple and compound eyes detect light, while compound eyes are especially sensitive to
movement. Two simple eyes are located anterior to the compound eyes. The third simple eye
is located on a ridge between the antennae.
4. Identify the mouth parts (Refer to Figure 2). The labrum is the hinged upper lip that is used
to hold food. The mandibles are crushing jaws. The maxillae are used to chew and taste
food. The labium is the broad, fat lower lip used to hold food while it is being chewed.
5. Label the mouthparts, eyes, and antenna on Figure 2 of your answer sheet.
6. Locate the eardrums or tympana, small drum-shaped structures on the first abdominal
segment.
7. All insects have six legs. In the grasshopper, the front pair is used for walking, climbing, and
holding food. The middle legs are used for walking and climbing. The hind legs are large and
enable the grasshopper to jump.
8. Locate the two pairs of wings.
9. Use a hand lens to look at the tiny openings along the abdomen. These are breathing pores
called spiracles through which oxygen enters and carbon dioxide leaves.
10. Label the tympanum and spiracles on Figure 1 of your answer sheet.
11. Determine if your grasshopper is a male or female by looking at the end of the abdomen.
Females have a tapered abdomen that ends in a pointed egg laying tube called the ovipositor.
Male have a more rounded abdomen that turns upward.
12. Label the ovipositor on Figure 1 of your answer sheet.
Procedure B: Internal Anatomy:
1. Examine the mouthparts, which are adapted for chewing on plants. Locate the labrum, or
upper lip. Beneath the labrum are two sets of jaws called the mandibles and the maxillae.
The mandibles are used for cutting, tearing, and crushing food. The maxillae are located
posterior to the mandibles and are used for cutting and holding food. Directly behind the
maxillae is the labium, or lower lip.
2. Using forceps, hold the base of each mouthpart and carefully remove it in the following order:
a) Pull the labrum upward
b) Pull the labium downward
c) Pull the mandible sideways
d) Pull the maxilla sideways
3. Examine the three pairs of legs and two pairs of wings attached to the thorax. The first two
pairs of legs are for walking and the last pair of legs is for jumping. The forewings have a
leathery appearance and protect the hind wings, which are made of broad membranes with
many veins.
4. Using forceps, remove one of the walking legs and one of the jumping legs. The coxa
connects the femur, the thickest section of the leg, to the grasshopper’s body. A slender,
spinytibia connects the femur to the tarsus, or bottom part of the leg.
5. Remove the three left legs. Insert the point of your scissors under the top surface of the last
segment of the abdomen. Make a cut to the left of the mid-dorsal line. Be careful not to cut the
organs underneath. In front of the thorax, cut down the left side to the bottom of the
grasshopper. Cut down between the next to the last and last abdominal segments.
WARNING: Always be careful with all sharp objects.
6. Use your forceps to pull down the left side. Locate the large dorsal blood vessel.
7. Use your scissors to cut the muscles close to the exoskeleton. Locate the finely branched
trachea leading to the spiracles.
8. Cut through the exoskeleton over the top of the head between the left antenna and left eye to
the mouth. Remove the exoskeleton on the left side of the head. Find the dorsal ganglion or
brain.
9. Cut away the tissue to show the digestive system. Refer to Figure 3 and identify the mouth,
esophagus, crop (storage area for food), gizzard (contains toothlike structures for grinding
and straining food), and stomach. Note that the gizzard and stomach are separated by a
narrow place. The digestive glands, called gastric caeca, that secrete enzymes into the
stomachare attached here.
10. Another narrow place separates the stomach from the intestine. Malpighian tubes, which
collect wastes from the blood, are located here.
11. Observe the colon, which enlarges to form the rectum. Wastes collect here before passing
outthe anus.
12. Observe the dorsal, tubular heart that extends through the first nine abdominal segments.
The heart is composed of a number of chambers, or enlargements.
13. Using a hand lens and a straight teasing needle or probe to move organs aside, find the
whitish ventral nerve cord on the inside ventral surface of the body cavity. Follow this
nerve cord along the entire length of the grasshopper’s body. Find the dorsal ganglion, or
brain, in the head of the grasshopper. Notice that the ventral nerve cord is connected to the
brain and branches on both sides of the esophagus to form a double ventral nerve cord
connected by fused ganglia.
14. In the female, the ovary is located above the intestines. The ovaries often contain masses of
large, yellow, oval-shaped eggs. In the male, a series of whitish tubes,the testes, are located
above the intestine.
15. WARNING: Give all dissected materials to your teacher for disposal. Always wash your
hands.
Name ______Date ______
Period ______
Grasshopper Dissection
Observations:
Figure 1: External Grasshopper Anatomy
Label the head, thorax, abdomen, walking legs, jumping legs, forewing, hind wing, tympanum, spiracles, ovipositor, coxa, femur, tibia, and tarsus
Figure 2: Grasshopper Head
Label the two compound eyes, three simple eyes (ocelli), antenna, labrum, mandible, maxilla, and labium.
Figure 3: Internal Grasshopper Anatomy
Label the mouth, esophagus, crop, gizzard, stomach, gastric caeca, Malpighian tubes, colon, rectum, anus, heart, ventral nerve cord, and brain.
1. Which region of the insect's body is specialized for sensory functions? Explain your answer.
______
______
______
2. Which region of the insect's body is specialized for movement & explain why?
______
______
______
3. What is the purpose of compound eyes? of simple eyes?
______
______
______
5. How are the ends of the legs adapted for holding onto plants?
______
______
______
6. How is the third pair of legs adapted for jumping?
______
______
______
7. How does the tympanic membrane help a grasshopper?
______
______
______
8. What system do spiracles open into on a grasshopper?
______
9. Do all abdominal segments have spiracles? Are there any spiracles on the thoracic segments?
______
______
______
10. How did you determine the gender of your grasshopper?
______
______
______