Comparing Arthropods Lab Reference Sheet
Segmented Body
Examine both the dorsal and ventral surfaces of the animals. Segmentation allows for sophisticated means of movement. It also allows an
animal to perform increasingly complex activities and use different segments to perform varying functions.
Type of Skeleton
Touch and lightly squeeze the animal. If the outside is hard, the animal has an external skeleton called an exoskeleton. They all have the same
type of skeleton, even though the exoskeleton of a spider is less rigid than the other two.
Modifications of Appendages
An appendage is any structure projecting from the main body of an animal having a specific appearance and function. Examples of human
appendages would be your nose, limbs, ears and hair. Appendages can be used for different types of movement, feeding behavior, sensory
detection and about anything else you can think of. Notice all the different types of appendages on each arthropod.
Jointed Appendages
Can the appendages bend at specific point? If so they are “jointed.”
Wings
Does the animal have wings?
Number of Body Regions
Examine the dorsal and ventral surface. Arthropods can have either three body regions: Head, thorax and abdomen or only two body regions:
Cephalothorax (head and thorax fused together) and abdomen.
Number of Eyes
Simple eyes (ocellus) are small and are usually located on the top and front of an arthropod’s head. They are simple in there is only one lens and
they detect light and dark. Compound eyes are usually located on the side of an arthropod’s head. They have multiple lenses to focus light and to
see clear images. You will need to look closely to determine what type(s) of eyes each animal has.
Number of Antenna Pairs
Antenna are paired sensory structures located on the head. Does the animal have antennae present? If so how many pairs of antennae does the
animal have?
Number of Leg Pairs
How many pairs of legs does each animal have? Count the large claw structures on the crayfish as legs but do not count the small leg like
appendages (swimmerets) on the ventral side of the abdomen as legs.