Download Grasshopper Dissection Introduction Insects are arthropods with

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. 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. 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.
Materials
gloves, dissecting tray, dissecting kit with forceps & scalpel/scissors, t-pins, magnifying glass, preserved grasshopper
Procedure (Part 1: External Anatomy)
1. Obtain a preserved grasshopper & rinse off any preservative with water. Place grasshopper in the dissecting tray.
2. Observe that the body of the grasshopper is divided into 3 regions --- the head, the thorax, and abdomen. Label these on
Figure 2.
3. Examine the head and locate the following parts:
a. Antennae (two, slender appendages)
b. Compound Eyes (2, large lateral)
c. Ocelli or Simple Eyes (3, small, between compound eyes)
d. Mouth Parts
i. Upper lip (labrum)
ii. Mandibles (jaws)
iii. Maxillae (located behind the mandibles to help cut & hold food)
iv. Lower lip (labium)
4. Label all mouthparts, eyes, and antenna on Figure 1.
5. Examine the following appendages on the thorax (middle section of the grasshopper's body):
a. Legs (first 2 pairs are for walking & the last pair are for jumping)
b. Wings (forewings have a leathery appearance & protect the hind wings)
6. Raise both pairs of wings and locate the first abdominal segment.
7. Locate the tympanic (auditory) membrane or eardrum on the first abdominal segment. Label this on Figure 2.
8. Using a magnifying glass, locate the spiracles or tiny pores for respiration on each side of the abdominal segments. Label
these on Figure 2.
9. 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. Label the ovipositor on Figure 2.
Procedure (Part 2: Internal Anatomy)
*** CAUTION: Always be careful with all sharp objects. ***
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Remove the legs and wings by GENTLY twisting and
pulling. Insert the point of your scissors under the
anterior surface of the last segment of the abdomen.
Make a cut along the dorsal surface. Be careful not to
cut the organs underneath. Refer to the diagram to the
right to landmark your cut.
Use your forceps to open up the grasshopper. Locate
the large dorsal blood vessel. This is actually the heart
and aorta. Label these on Figure 3.
Use your scissors to cut the muscles close to the
exoskeleton. Attempt to locate the finely branched
tracheal tubes leading to the spiracles.
Cut away the tissue to show the digestive system.
Identify the mouth, esophagus, crop, and stomach. The
digestive glands, called gastric caeca, that secrete
For study of
enzymes into the stomach are located between the
internal
crop and the stomach. Label all parts on Figure 3.
anatomy, make
Another narrowing separates the stomach from the
a cut along the
intestine. Malpighian tubules, which collect wastes
dashed line.
from the blood, are located here. Label them on Figure
3.
Observe the intestine, which enlarges to form the
rectum. Wastes collect here before passing out the
anus. Label these on Figure 3.
In the female, the ovary is located above the intestines.
In the male, a series of whitish tubes, the testes, are
located above the intestine.
Cut through the exoskeleton over the top of the head
between an antenna and eye down to the mouth.
Remove the exoskeleton on this side of the head. Find the dorsal ganglion or brain. Label it on Figure 3.
Optional: Using a scalpel, shave a thin section from the front of the compound eye of your grasshopper. Place the section
on a microscope slide, add a drop of water, and place a cover slip on top. Observe the slide under the microscope.
Complete a biological drawing below.
Clean Up and Disposal
1. Once your group has finished observing and identifying the structures of the grasshopper, it must be disposed of safely. If
there are any excess fluids in your dissecting tray, please pour them down the sink with plenty of water.
2. Place all grasshopper and grasshopper tissues directly into the garbage bag/biohazard bin provided by your teacher.
3. Wash your dissecting instruments and dry them to prevent rusting.
4. Placing dissecting instruments back into the kit/tray only when fully dry.
5. Wash out the dissecting tray with soapy water and lay them on a common bench to drip dry.
6. Dispose of your gloves in the garbage and wash your hands thoroughly.
Observations
Figure 1: Grasshopper Head
Figure 2: External Grasshopper Anatomy
Figure 3: Internal Grasshopper Anatomy
Discussion
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 your answer.
3.
How does the tympanic membrane help a grasshopper?
4.
What system do spiracles open into on a grasshopper? Which segments of the grasshopper’s body contain spiracles?
5.
What sex was your grasshopper? How did you determine this?
6.
Fill in the following table regarding the grasshopper internal anatomy.
Structure
Function
Anus
Aorta
Crop
Esophagus
Ganglion
Gastric Caeca
Heart
Intestines
Malpighian Tubules
Mouth
Ovaries
Rectum
Stomach
Testes
Trachea
System