The animal Phylum Arthropoda includes many, many species, who share a few characteristics: their body / muscle support is on the outside, in the form of an exoskeleton which covers their whole bodies, and is jointed at flexing points; they generally have many pairs of legs; they circulate blood through their hollow interior, through what is called an open circulatory system; they, like many other invertebrate groups, have a nervous system whose central cord is paired and solid and runs along their ventral (belly) surface. They include arachnids, like spiders, scorpions, ticks, and mites, and two groups we'll look at in the lab - the crustaceans, mostly aquatic, and the insects, which are mostly terrestrial and usually winged.
Crayfish are common freshwater crustaceans, related to lobsters, crabs, and shrimp.
They are bottom dwellers and live as predators and scavengers. They live in small hollows or burrows that they back into, with their chelipeds , or claws, facing out.
External Anatomy. There is a sheet with labeled drawings to help you identify the structures. Crayfish, like all crustaceans, are also characterized by doubled, or biramous appendages - note that, although the main antennae are single, the shorter antennules below them are doubled; we'll also later see doubled structures at the bases of the legs.
1. The front legs, the chelipeds , are supposed to be a specialized adaptation of one of the sets of regular walking legs - this means that the chelipeds and the walking legs are homologous, built from the same basic structure. Look closely at them - what similarities support this idea?
2. The cheliped, of course, is not a walking leg - it's adapted for defense and for grabbing prey. How is it different from a walking leg?
3. Arthropods are considered to be segmented - their basic body plan, at least as embryos, consists of repeating units. Some of this feature remains visible on the outside. What parts of the crayfish body show signs of segmentation?
4. What parts of the crayfish do not seem to be segmented?

Inspect the swimmerets - they are the fine, leglike (they are also modified legs) structures under the abdomen, behind the walking legs. In females, they all look roughly the same, but males have much larger anterior ones which are used to transfer sperm packets from the male's genital opening (a small pipelike structure just in front of the swimmerets, usually difficult to see) to the female's. The female receives sperm in the autumn and stores it in a seminal receptacle until the following spring - she then lays her eggs and deposits the sperm on them. The fertilized eggs (and the larvae that hatch from them) are then carried around attached to the mother's swimmerets for as long as three months.
5. Which gender is your crayfish specimen?
6. Is fertilization in crayfish external or internal?
Explain briefly.
Carefully pry up the carapace, the shield-like covering, and cut it away from the crayfish. This should expose the gills. When out of the water, a crayfish can continue to breathe as long as it can keep some water trapped in there around the gills.
7. How many sets of gills are there on one side?
Grasshoppers are insects , the largest arthropod subgroup. There are more named insect species than in any other group of animals; whether there are more actual species is much more difficult to determine. Insects are considered a terrestrial, or land, group. Grasshoppers are a type of herbivorous (plant-eating) insect from an order that includes crickets, mantises, and cockroaches.
Our specimens are from a particularly large species of grasshoppers, commonly called "lubbers."
External Anatomy.
Get a preserved grasshopper specimen. The bodies of insects are divided into three sections: the head , with many of the sensory organs, the main processors / brain, and the mouth; the thorax , with its six legs (insects characteristically have six and only six true legs) and, in most adults, four wings (although wings have often been adapted as protective covers); and the abdomen, which usually carries the sex organs.
1. Compare. How are the grasshopper's external features similar to those of the crayfish?
2. Contrast. How are the grasshopper's external features different from those of the crayfish?
The Head.
Locate the large compound eyes.
Arthropod eyes typically don't have one big lens in front of a screen of detectors, like our eyes - they have a layer of small lenses, each with a small set of detectors. This takes up much less space. Grasshoppers do have three single-lens eyes, above and

between the bases of the antennae. The antennae are used for other senses, such as touch and some parts of the sense of smell. Take a razor blade and carefully make a small shaving from the surface of the eye. Mount the slice on a microscope slide (dry) and look at it at low and/or medium power, or at high magnification under the dissecting ‘scope.
3. Describe the appearance of your slice of compound eye.
Around the mouth opening are a number of different types of mouthparts . Like a crayfish's chelipeds (and some crayfish mouthparts), several of these are modified legs. Note the somewhat leglike palps that help move food around, the plates that provide a kind of "cheek" cavity, and the tongue-like hypoglottis and grabbing and chewing mandibles in the actual mouth opening.
The Thorax. The thorax is derived from three original segments, each with a pair of legs; the last two, in many forms (but virtually always only in the adult stage) also support wings. The thorax is usually very solidly built, to support the power of the walking and flying muscles. In many insects, the grasshopper included, the front set of wings may be very different from the back set. Compare and contrast the wings in your grasshopper - be sure to spread the back wings. If your specimen is not an adult, the wings are not developed and may be small and difficult to do this with.
4. The front wings:
5. The back wings:
The Abdomen.
On the first abdominal segment, just behind and below each wing, is a structure called the tympanum.
Humans have a similar structure with the same name and function (but it's not on our abdomens).
6. Describe the grasshopper's tympanum.
7. The tympanum contains many nerves and processors. It picks up vibrations carried in the air.
Why?
Grasshoppers, as most insects do, breathe through a tracheal system, an organization of tubes that connect the cells of the body directly with the outside air. The blood carries almost no oxygen. The openings for the system, spiracles, can be seen along the sides of the thorax and abdomen. Also, the reproductive structures are on (and in) the abdomen. Female insects can often be recognized by their ovipositors - structures specialized for laying eggs. Since grasshoppers dig a shallow hole for a packet of eggs, the ovipositor is a large spade / pusher, and only seen on the female.
8. Is your grasshopper male or female?

(hand collected in Venezuela)
Observe on your own and make a list of 10 observations using the following information.
Description
All scorpions have a long, slender body with a five-segmented tail that can be arched over the back. The tail ends in a bulb-like poison gland or stinger. Scorpions have four pairs of legs and two large pincer-bearing arms
(pedipalps) in front. Scorpions are well equipped to defend themselves or attack prey with their pincers and stinger. Between the last pair of legs is a comblike structure (pectines) that is used to identify surface textures and to detect prey.
Scorpions have two eyes on the top of the head, and usually two to five pairs of eyes along the front corners of the head. They do not see well, however, and must rely on the sense of touch, using their pectines and other organs for navigation and hunting. Their bodies are flat, which allows them to hide in small cracks, under rocks and under bark.
Worldwide, scorpions range in size from ½ inch to 7 1/4 inches long (including the tail) depending on the species. The most common species in Texas is the striped bark scorpion, Centruroides vittatus . The adult scorpion is about 2 ½ inches long, which is typical of the size of all species found in the state.
Biology
Scorpions hide during the day and become active at night. This behavior helps scorpions manage temperature and water balance, important functions for survival in dry habitats. Many species dig burrows in the soil. They detect and capture prey by the sense of touch. They also have a well-developed sense of hearing.
Scorpions hide under stones, bark, wood or other objects on the ground where they wait or search for prey.
Chief foods are small insects, spiders, centipedes, earthworms, and other scorpions. Once they capture their prey, they use the large pincers to crush and draw it toward the mouth. The body juices of the prey are eaten by the scorpion.
Some species may live for 20 to 25 years, but longevity of the typical scorpion is between 3 and 8 years.
Adult scorpions may have several broods of young. Following an elaborate mating process, which lasts from 24 to 36 hours, the female undergoes a gestation period ranging from 5 months to more than 1 year. The young are born alive in semi-transparent sacs. As soon as the young scorpions free themselves from these thin wrappers, they climb onto their mother's back. Already capable of stinging, the young scorpions leave the mother after several days and begin to fend for themselves. Scorpions reach maturity in a year or more, depending on availability of food.
The sting of scorpions may be painful, or even deadly, depending on the species. Of 1,500 species of scorpions worldwide, only about 20 to 25 are regarded as dangerous. Stings from such species may cause paralysis, severe convulsions, cardiac irregularities, or breathing difficulties that may lead to death. Antivenins are available in areas where dangerous scorpions live.

A scorpion's venom is a mixture of compounds including neurotoxins that affect the victim's nervous system.
Fortunately, none of the species in Texas are considered deadly. Stings from most of these species are about as painful as a bee or wasp sting, but the severity of the sting is dependent upon the individual scorpion and the person's reaction to the venom. As with any arthropod venom, allergic reactions are possible. In these situations, immediate medical attention would be required.
Habitat
Scorpions may be found in many types of habitats in the United States, including desert flats, sand dunes, desert and mesic mountains, grasslands, pine forests, deciduous forests, and chaparral. Species are most diverse in desert areas.

JBHA 7 Arthropod Lab Name________________
TO DO TO DO TO DO TO DO TO DO TO DO TO DO TO TO TO DO DO TO DO
Create a Model or Design an Illustration (drawing) of an Arthropod which could fit into any real or imaginary environment, such as one which can live under water and also fly; one which would live on mars, or in the ocean on the moon of Jupiter called Europa; or one of your choice.
1.
To which class does your arthropod belong?
2.
What are the scientific and common names of your new arthropod? Be creative, but use names that describe your arthropod well.
3.
Describe its natural habitat.
4.
How many appendages does it have? What are they specialized for?
5.
Does your arthropod have spiracles? Where are they located?
6.
Does your arthropod have antennae? What are they used for?
7.
What does it eat? Is it a carnivore, herbivore, or omnivore?
8.
Describe the changes your Arthropod goes through during its life cycle. Draw and label its complete life cycle.
9.
What are some of the specific adaptations that your Arthropod has and how does that help it in its particular environment?
10.
Is your arthropod harmful or useful to the environment? Explain your answer
Or
go to the Reference Links below and briefly describe each of the following:
1. ARTHROPODS
Joint-legged animals without backbones are called arthropods and are placed in the phylum Arthropoda. Human legs are jointed at the knees
2. Arthropods
Arthropods are animals with segmented bodies and six or more jointed legs. They are the largest animal group
3. Images of Arthropods
A great selection Arthropod Images
4. Introduction to the Arthropoda
By nearly any measure, the most successful animals on the planet are the arthropods. They have conquered land, sea and air, and make up over three-fourths of all currently known living and fossil organisms
5. Milli-CAM
A millipede cam, inlcudes other millipede images.
6.
The Dynastes granti Beetle
The largest beetle species found in the United States

Crayfish abdomen - the segmented tail area of a grasshopper, which contains the heart, reproductive organs, and most of the digestive system antennae - like all insects, grasshoppers have 2 segmented antennae that sense touch and odors compound eye - grasshoppers have 2 faceted eyes made up of many hexagonal lenses head - the head is at the front end of the grasshopper's body and is the location of the brain, the two compound eyes, the mouth parts, and the points of attachment of its two antennae. jumping legs -the long, hindmost pair of the grasshopper's six legs mandibles - the jaws, located near the tip of the head, by the palps; the jaws crush the food palps - long, segmented mouth parts
(under the jaws) that grasp the food spiracles - a series of holes located along both sides of the abdomen; they are used for breathing thorax - the middle area of the grasshopper's body - where the legs and wings are attached walking legs - the four, short front legs that are used for walking wings - grasshoppers have two long wings, used for flying.