Biology 2

Grasshopper Dissection Lab


If you missed the dissection lab, click HERE for a video that details the exact same dissection techniques that were done in class.



Insects are arthropods with jointed appendages, segmented bodies, and an exoskeleton composed of chitin.  Insects belong to the Class Insecta, and are the largest and most diverse group of animals on earth.  The genus Romalea is a large grasshopper common in the southeastern United States.  The common name for this grasshopper is the Eastern Lubber Grasshopper.  The scientific name for this grasshopper is Romalea guttata.  There are several other versions of this name (Romalea micropetera), but this is the current and most acceptable name.  This is the type of grasshopper you will be dissecting today.


Insects have three body regions (head, abdomen, and thorax), 3 pairs of legs attached to the thorax, a single pair of antenna attached to the head, mouthparts adapted for chewing (like the grasshopper) or sucking, and 2 pairs of wings.  Some insects may have a single pair of wings, while others may be wingless.  The grasshopper has two pairs of wings.  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 abdomen 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.




Grasshoppers have the typical insect body plan of head, thorax and abdomen. The head is held vertically at an angle to the body, with the mouth at the bottom. The head bears a large pair of compound eyes which give all-round vision, three simple eyes which can detect light and dark, and a pair of thread-like antennae that are sensitive to touch and smell. The downward-directed mouthparts are modified for chewing and there are two sensory palps in front of the jaws.


The thorax and abdomen are segmented and have a rigid cuticle made up of overlapping plates composed of chitin. The three fused thoracic segments bear three pairs of legs and two pairs of wings. The forewings, known as tegmina, are narrow and leathery while the hindwings are large and membranous, the veins providing strength. The legs are terminated by claws for gripping. The hind leg is particularly powerful; the femur is robust and has several ridges where different surfaces join and the inner ridges bear stridulatory pegs in some species. The posterior edge of the tibia bears a double row of spines and there are a pair of articulated spurs near its lower end. The interior of the thorax houses the muscles that control the wings and legs.


The abdomen has ten segments, the first of which is fused to the thorax and contains the tympanal organ and hearing system. Segments two to eight are ring-shaped and joined by flexible membranes. Segments nine and ten are reduced in size; segment nine bears a pair of cerci and segment ten has the reproductive organs. Female grasshoppers are normally larger than males, with short ovipositors. The name of the suborder "Caelifera" comes from the Latin and means chisel-bearing, referring to the shape of the ovipositor.


Those species that make easily heard noises usually do so by rubbing a row of pegs on the hind legs against the edges of the forewings (stridulation). These sounds are produced mainly by males to attract females, though in some species the females also stridulate.

Grasshoppers may be confused with crickets, but they differ in many aspects; these include the number of segments in their antennae and the structure of the ovipositor, as well as the location of the tympanal organ and the methods by which sound is produced. Crickets have antennae that can be much longer than the body and have at least 20–24 segments, while grasshoppers have fewer segments in their shorter, stouter antennae.


Diet and digestion:

Most grasshoppers are polyphagous, eating vegetation from multiple plant sources, but some are omnivorous and also eat animal tissue and animal feces. In general, their preference is for grasses, including many cereals grown as crops. The digestive system is typical of insects, with Malpighian tubules discharging into the midgut. Carbohydrates are digested mainly in the crop, while proteins are digested in the ceca of the midgut. Saliva is abundant but largely free of enzymes, helping to move food and Malpighian secretions along the gut. Some grasshoppers possess cellulase, which by softening plant cell walls makes plant cell contents accessible to other digestive enzymes.



Sensory organs:

Grasshoppers have a typical insect nervous system and have an extensive set of external sense organs. On the side of the head are a pair of large compound eyes which give a broad field of vision and can detect movement, shape, color and distance. There are also three simple eyes (ocelli) on the forehead which can detect light intensity, a pair of antennae containing olfactory (smell) and touch receptors, and mouthparts containing gustatory (taste) receptors. At the front end of the abdomen there is a pair of tympanal organs for sound reception. There are numerous fine hairs (setae) covering the whole body that act as mechanoreceptors (touch and wind sensors), and these are most dense on the antennae, the palps (part of the mouth), and on the cerci at the tip of the abdomen. There are special receptors (campaniform sensillae) embedded in the cuticle of the legs that sense pressure and cuticle distortion. There are internal "chordotonal" sense organs specialized to detect position and movement about the joints of the exoskeleton. The receptors convey information to the central nervous system through sensory neurons, and most of these have their cell bodies located in the periphery near the receptor site itself.



Circulation and respiration:

Like other insects, grasshoppers have an open circulatory system and their body cavities are filled with hemolymph. A heart-like structure in the upper part of the abdomen pumps the fluid to the head from where it percolates past the tissues and organs on its way back to the abdomen. This system circulates nutrients throughout the body and carries metabolic wastes to be excreted into the gut. Other functions of the hemolymph include wound healing, heat transfer and the provision of hydrostatic pressure, but the circulatory system is not involved in gaseous exchange. Respiration is performed using tracheae, air-filled tubes, which open at the surfaces of the thorax and abdomen through pairs of valved spiracles. Larger insects may need to actively ventilate their bodies by opening some spiracles while others remain closed, using abdominal muscles to expand and contract the body and pump air through the system.




A large grasshopper, such as a locust, can jump about a meter (twenty body lengths) without using its wings; the acceleration peaks at about 20 g. Grasshoppers jump by extending their large back legs and pushing against the substrate (the ground, a twig, a blade of grass or whatever else they are standing on); the reaction force propels them into the air. They jump for several reasons; to escape from a predator, to launch themselves into flight, or simply to move from place to place. For the escape jump in particular there is strong selective pressure to maximize take-off velocity, since this determines the range. This means that the legs must thrust against the ground with both high force and a high velocity of movement. A fundamental property of muscle is that it cannot contract with high force and high velocity at the same time. Grasshoppers overcome this by using a catapult mechanism to amplify the mechanical power produced by their muscles.


The jump is a three-stage process. First, the grasshopper fully flexes the lower part of the leg (tibia) against the upper part (femur) by activating the flexor tibiae muscle (the back legs of the grasshopper in the top photograph are in this preparatory position). Second, there is a period of co-contraction in which force builds up in the large, pennate extensor tibiae muscle, but the tibia is kept flexed by the simultaneous contraction of the flexor tibiae muscle. The extensor muscle is much stronger than the flexor muscle, but the latter is aided by specializations in the joint that give it a large effective mechanical advantage over the former when the tibia is fully flexed. Co-contraction can last for up to half a second, and during this period the extensor muscle shortens and stores elastic strain energy by distorting stiff cuticular structures in the leg.  The extensor muscle contraction is quite slow (almost isometric), which allows it to develop high force (up to 14 N in the desert locust), but because it is slow only low power is needed. The third stage of the jump is the trigger relaxation of the flexor muscle, which releases the tibia from the flexed position. The subsequent rapid tibial extension is driven mainly by the relaxation of the elastic structures, rather than by further shortening of the extensor muscle. In this way the stiff cuticle acts like the elastic of a catapult, or the bow of a bow-and-arrow. Energy is put into the store at low power by slow but strong muscle contraction and retrieved from the store at high power by rapid relaxation of the mechanical elastic structures.



Male grasshoppers spend much of the day stridulating, singing more actively under optimal conditions and being more subdued when conditions are adverse; females also stridulate, but their efforts are insignificant when compared to the males. Late-stage male nymphs can sometimes be seen making stridulatory movements, although they lack the equipment to make sounds, demonstrating the importance of this behavioral trait. The songs are a means of communication; the male stridulation seems to express reproductive maturity, the desire for social cohesion and individual well-being. Social cohesion becomes necessary among grasshoppers because of their ability to jump or fly large distances, and the song can serve to limit dispersal and guide others to favorable habitat. The generalized song can vary in phraseology and intensity and is modified in the presence of a rival male, and changes again to a courtship song when a female is nearby. In male grasshoppers of the family Pneumoridae, the enlarged abdomen amplifies stridulation.


Life cycle:

In most grasshopper species, conflicts between males over females rarely escalate beyond ritualistic displays. Some exceptions include the chameleon grasshopper (Kosciuscola tristis), where males may fight on top of ovipositing females, engaging in leg grappling, biting, kicking and mounting.


The newly emerged female grasshopper has a preoviposition period of a week or two while she increases in weight and her eggs mature. After mating, the female of most species digs a hole with her ovipositor and lays a batch of eggs in a pod in the ground near food plants, generally in the summer. After laying the eggs, she covers the hole with soil and litter. Some, like the semi-aquatic Cornops aquaticum, deposit the pod directly into plant tissue. The eggs in the pod are glued together with a froth in some species. After a few weeks of development, the eggs of most species in temperate climates go into diapause and pass the winter in this state. Diapause is broken by a sufficiently low ground temperature, with development resuming as soon as the ground warms above a certain threshold temperature. The embryos in a pod generally all hatch out within a few minutes of each other. They soon shed their membranes and their exoskeletons harden. These first instar nymphs can then jump away from predators.


Grasshoppers undergo incomplete metamorphosis: they repeatedly molt, each instar becoming larger and more like an adult, with the wing-buds increasing in size at each stage. The number of instars varies between species but is often six. After the final molt, the wings are inflated and become fully functional. The migratory grasshopper, Melanoplus sanguinipes, spends about 25 to 30 days as a nymph, depending on sex and temperature, and lives for about 51 days as an adult.


Anti-predator defenses:

Grasshoppers exemplify a range of anti-predator adaptations, enabling them to avoid detection, to escape if detected, and in some cases to avoid being eaten if captured. Grasshoppers are often camouflaged to avoid detection by predators that hunt by sight; some species can change their coloration to suit their surroundings.

Several species such as the hooded leaf grasshopper Phyllochoreia ramakrishnai (Eumastacoidea) are detailed mimics of leaves. Stick grasshoppers (Proscopiidae) mimic wooden sticks in form and coloration. Grasshoppers often have deimatic patterns on their wings, giving a sudden flash of bright colors that may startle predators long enough to give time to escape in a combination of jump and flight.


Some species are genuinely aposematic, having both bright warning coloration and sufficient toxicity to dissuade predators. Dictyophorus productus (Pyrgomorphidae) is a "heavy, bloated, sluggish insect" that makes no attempt to hide; it has a bright red abdomen. A Cercopithecus monkey that ate other grasshoppers refused to eat the species. Another species, the rainbow or painted grasshopper of Arizona, Dactylotum bicolor (Acridoidea), has been shown by experiment with a natural predator, the little striped whiptail lizard, to be aposematic.




Eastern Lubber Grasshopper Phylogeny:

Kingdom = Animalia

Phylum = Arthropoda

Class = Insecta

Order = Orthoptera

Family = Romaleidae

Genus = Romalea

Species = guttata or microptera

Eastern Lubber Grasshopper scientific name:  Romalea guttata* or Romalea microptera

 *the species we are dissecting is most likely the Romalea guttata


Dissection Lab Objectives:

1.     Identify and label the external anatomical structures of the common grasshopper.

2.     Identify and label the internal anatomical structures of the common grasshopper.



Materials Needed:

1.      dissection tray

2.     dissection tools (small scissors, tweezers, probes, scalpel)

3.     about 10 T-pins

4.     preserved grasshopper


Dissection Procedure Part One:  The External Anatomy

1.     Obtain a preserved grasshopper and rinse off any preservative residue with water.  Place grasshopper in the dissecting tray. 


2.     Observe that the body is divided into three regions:  Head, Thorax, and Abdomen.  Carefully observe where each region begins and ends. 


3.     Use the diagram below to help you identify the basic external features of the grasshopper.  Try to locate each item on your grasshopper that is listed below.




4.     Use the diagrams below and on the next page to help you locate the structures found on the head of your grasshopper.  Try to identify each item on your grasshopper that is shown below in the diagrams.





          1. Labrum

         4. Labium

          2. Mandibles

         5. Maxillary Palps

          3. Labial Palps

         6. Maxillae

          7. compound eye

         8. ocelli



5.     Use the diagram below to help you identify the different divisions of the thorax (prothorax, metathorax, and mesothorax).  Find these areas on your grasshopper specimen.




6.     Locate the pronotum.  This is the shield-like structure that protects much of the thorax region of the grasshopper.  See the diagram below to help you locate this structure.


7.  The following appendages are also located on the thorax of the grasshopper:


prothorax contains the landing legs

mesothorax contains the walking legs and the forewings

metathorax contains the jumping legs and the hindwings



8.   Below are two diagrams showing the names and locations of the parts of an insect’s leg.  Make sure that you are able to identify these parts on the jumping leg of your specimen.


Profile of grasshopper leg section. | Download Scientific Diagram


9.   Below is a diagram that shows the difference between male and female grasshoppers.  The main difference is the structure known as the ovipositor.  Only females have these structures.  They function to help in the egg laying process.  It is used to prepare a place for the placement of the eggs in the sand or dirt. 


female grasshopper


male grasshopper



10.   Locate the tympanum (sometimes called the tympanic membrane).  This is usually a small oval-like area above the base of the jumping leg and below the hind wing joint.  This is what the grasshopper uses to hear soundwaves.  Use the diagram below to help you locate this sense organ.  Also locate the spiracles.  These are used for gas exchange and can be seen on your specimen by using a magnifying glass.





Dissection Procedure Part Two:  The Internal Anatomy


1.     Place the grasshopper in the tray with the dorsal side up and the ventral side down (so it looks like it might just walk away). 


2.     Locate the pronotum and using the small pointed tip of the smallest scissors you can find, gently place the tip underneath the pronotum and cut upward towards the head until you have dissected the pronotum into two halves.  Be careful as to not cut too deeply, just use small snips.


3.     Next find the junction where the exoskeleton begins on the dorsal part of the abdomen.  Gently cut downwards towards the anus.  Again, pay special attention so as not to cut too deeply.  Once you have cut open the thorax and the abdomen, pin them open so that you can view the items inside the cavities you just opened up.


4.     Use the diagram below to help you locate the internal organs of the grasshopper.



5.     If you have a female grasshopper, the small rice-like looking structures are the eggs.  You may have to remove these before you can see the major internal organs.


6.     You will be responsible for finding these items on your grasshopper:



gastric ceca

malpighian tubules



7.     Dispose of the grasshopper and clean up your area.


 Click HERE for the Grasshopper Lab Companion.  Use this as a means to prepare for the lab quiz.