Grasshopper Lab 

by E. S. Belasic

Objectives:

• to observe the external anatomy of a grasshopper. 
• to determine the sex of a grasshopper using external anatomy.
• to collect statistical data on grasshopper length

Procedure:

External Anatomy:

1. Look for the presence of an ovipositor (female) and record the sex of your grasshopper into Table 1.
2. Measure your grasshopper's length in cm from the most anterior point (antennae) to the most posterior (end of abdomen) then record in Table 1.
3. Straighten the right jumping leg and measure the complete length in cm, then record in Table 1.
4. Draw and label the head, thorax, abdomen, legs, and wings, anterior, posterior, dorsal, & ventral in Figure 1.
5. Find the tympanum on the grasshopper.  Note the locations. Draw and label  in Figure 2.
6. Look at the abdomen, see if you can find the spiracles on each segment.  Draw and label  in Figure 2 also.
7. Look at the head.  Find and label the following parts : 3 simple eyes (ocelli), compound eyes, antennae, mouth parts in Figure 3.

Data: (leave a 1/2 page for each figure and table)

Table 1: Data Table of Grasshopper Information

Length of grasshopper	cm
Length of right jumping leg	cm
Sex of Grasshopper	(male or female)

Figure 1: External anatomy diagram of the grasshopper. Lateral View.
               Label the head, thorax, abdomen, legs, wings, anterior, posterior, dorsal, & ventral.

Figure 2: Diagram of the Grasshopper tympanum.

Figure 3: Diagram of head. Label simple eyes, compound eyes, antennae, mouth parts

Figure 4: Double Stem and Leaf of Grasshopper Body and Leg Length in cm

Table 2: Summary Data Table of Grasshopper Lengths

	Grasshopper Length in cm	Length of Right leg in cm
n
max
min
range
sum
mean
median
Q3
Q1
IQR

Figure 5: Stacked Box Plot of Grasshopper Body Length and Right Leg Length

Analysis/Results:

1. What is the function of the tympanum? Where is it located?
2. Which sex has an ovipositor? What is its function?
3. What type of mouth parts do grasshoppers have? How about Metamorphosis?
4. Describe the function of the spiracles.  Why don't grasshoppers have gills or lungs?
5. What was the median size in cm of our grasshoppers? Was there a wide variety in sizes? Explain.
6. Is there a mathematical relationship between leg length and body length? Look at your Box Plot.
7. Compare and contrast the grasshopper to the crayfish.  List 2 similarities and 2 differences.

Conclusion: 2-3 sentences on what you learned

GRASSHOPPER DISSECTION

 
INTRODUCTION: 
 Like other arthropods, the insects possess segmented bodies,
jointed appendages, and a chitinous exoskeleton, but as a class,
they are distinguished by having one pair of antennae and a body
of three conspicuous subdivisions: head, thorax, and abdomen. 
Typically, the thorax bears three pairs of legs and two pairs of
wings, some have only one pair of wings and others are wingless. 
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
mouth parts are adapted either for chewing or sucking, and they
feed variously on plant or animal materials.
 
PURPOSE: To study the internal and external anatomy of the
  grasshopper.
 
CLASSIFICATION:
 Kingdom - Animalia
 Phylum - Arthropoda
 Class - Insecta
 Order - Orthoptera
 
MATERIALS: A preserved specimen, dissecting pan, scalpel or
 razor blade, scissors, probe, hand lens
 
 
EXTERNAL DISSECTION
 
 Examine the entire grasshopper and identify the major
subdivisions and parts of the body. The parts that are starred
are to be dissected out and taped on a sheet of white paper with
Scotch tape. Properly identify and label each part.
 
 HEAD ABDOMEN
*Antennae (2, slender) *Spiracles (small openings
*Compound eyes (2, large lateral) on side of somites)
*Ocelli (or simple eyes) * Auditory Organs (2, 
 3, small, between cpd eyes lateral on 1st somite)
*Mouth parts * Ovipositor (on female)
 do these last if time 
 permits
 
 THORAX
*Legs (3 pairs)
*Wings (2 pairs)
 
INTERNAL DISSECTION
 
 With scissors and beginning at the tip of the abdomen, make
an incision (lengthwise) in the body covering slightly to the
left of the middorsal line and along the entire length of the
grasshopper. Make a similar cut ventrally and also up the front
of the head. Keep the inner scissors point just inside the body
covering to avoid damaging the internal organs. If the specimen
is a mature female, the interior spaces may be filled largely
with slender eggs in the ovaries. Remove some of these is so
directed by the instructor.
 
 Locate the following organ systems:
 
1. Integument and exoskeleton
2. Muscular - In studying the other systems, note the many 
 muscles, especially those connecting the wings and the
 legs.
3. Digestive system - remove some of the lateral muscles and
trachea as necessary without injuring other organs. Identify the
following structures in the digestive system.
 a. *Esophagus d. *Gastric caeca g. *Rectum
 b. *Crop e. *Stomach h. *Anus
 c. *Gizzard f. *Intestine
 
4. Circulatory system - heart
5. Respiratory system - tracheae
6. Excretory system - Malpighian tubules
7. Nervous system - brain, nerve cord
8. Reproductive system - testes, *ovaries, oviduct

The Grasshopper (Romalea sp.)

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Romalea sp. is a large grasshopper common in the southeastern United States. Its main habitat is open grassland, weed patches and roadside growth where it eats grasses and other vegetation.

Obtain a preserved grasshopper and place it in your dissection pan. The grasshopper belongs to the Class Insecta which is characterized by having three body regions (head, thorax and abdomen), one pair of antennae, and six legs (see Figure 7 ). Romalea has 10 abdominal segments, the terminal abdominal segment bears the reproductive genitalia. The terminal segment of males is blunt, whereas that of females is modified to lay eggs and is called an ovipositor (see Figure 7). Determine the sex of your grasshopper.

Position your grasshopper dorsal side upward and cut along the dorsal surface of the thorax and abdomen and pull the exoskeleton aside. Be sure to keeep your scissors close to the body wall to avoid damage to the internal structures. The digestive system fills most of the internal cavity of the grasshopper (except in mature females which may be filled with eggs). A muscular tube, the esophagus, conveys food from the pharynx into a large storage organ, the crop. Chewed food is stored in the crop. Next is the stomach to which are attached six double fingered-shaped digestive glands, the gastric caecae, which produce enzymes that are secreted into the stomach to aid in digestion. Because most of the digestive tract is lined with chiton (except the stomach and crop) digestion and absorption take place mainly in the stomach. The digestive tract continues as the intestine, a thin tube without accessory structures. It leads to the short rectum which opens to the exterior via the anus. The hair-like tubules lying over the intestine are Malphighian tubules, the excretory organs.

The sexes of the grasshopper are separate, and their reproductive organs are in the terminal abdominal segments (see Figure 7 ). In the male, each of the two testes is composed of a series of slender tuules, follicles, and is located above the intertine. Each testis is joined to a longitudinal vas deferens. The vas deferens are joined to a single ejaculatory duct to which accessory glands are attached. In the female, each ovary is composed of several tapering egg tubes which produce the ova. Each ovary is joined to an oviduct leading to the vagina, to which a pair of accessory glands and a single spermatheca are attached. The latter organ is used to store sperm received at copulation.

Figure 7: The grasshopper

A- external anatomy

This image was obtained from the Biodidac image data base maintained at the University of Ottawa. Click here and check out this wonderful site.

B- internal anatomy