Download The internal anatomy of insects will only be studied in lecture.

Zoology
Exercise #15: Hexapods
Lab Guide
Insects are the largest group of animals. Among the chief characteristics are 3 pairs of walking legs, one pair of antennae and
a body that is typically divided into head, thorax, and abdomen. Their respiratory system is composed of tracheal tubes. Most
are also provided with one or two pairs of wings. Their sense organs are often specialized and perhaps account for much of
their success in the competition for places to live. Most are less than 2.5cm long, but can range from 1cm to 20cm.
External Anatomy
The division of the body consists of 3 tagmata: head, thorax, and abdomen. The chitinous exoskeleton is secreted by the
underlying epidermis. It is composed of hard plates, called sclerites. These sclerites are bound by areas of soft cuticle.
The head of the grasshopper, our representative insect, is freely movable. They have compound eyes, antennae, and ocelli.
One ocelli is most likely dorsal to the base of each antennae and one in the groove between them. They have a bilobed upper
lip, or labrum and a toothed mandible. The mouth consists of a membranous hypopharynx for tasting food. There is a
bilobed lower lip called a labium. It is a result of a fusion of the second maxillae. On each side of the labium is a 3 jointed
labial palp. Between the mandible and labium are paired maxillae. Each has a maxillary palp, flat lobe, and a toothed jaw.
These mouthparts in grasshoppers are adapted for biting and chewing.
Overall, there are 4 pairs of true appendages: antennae, mandibles, maxillae, and labium (fusion of the second maxillae).
The thorax is made up of 3 segments: prothorax, mesothorax, and metathorax. Each bears a pair of legs. The mesothorax
and metathorax also bear a pair of wings. Spiracles, which are openings to the insects tracheal system, are located above the
legs in the mesothorax and metathorax. The forewings are leathery (on the mesothorax) and the hindwings are
membranous (on the metathorax). The legs are divided in segments: coxa, trochanter, femur, tibia, tarsus, claws and
arolium.
The abdomen has 11 segments. There is a large tympanum which is the organ for hearing. One is located on each side of the
first abdominal segment. The eleventh segment forms the genitalia (secondary sex organs). On each side, behind the tenth
segment, is a projection, the cercus. In females the posterior end of the abdomen is pointed and consists of two pairs of plates,
with a smaller pair between, with the entire thing forming the ovipositor.
Internal Anatomy
The internal anatomy of insects will only be studied in lecture.
Procedure
External
1. You will be studying a preserved specimen of grasshopper. A hand lens is EXTREMELY IMPORTANT to you success in
this lab for viewing these very small structures. Place the preserved grasshopper in your dissecting tray and make observations of
the following parts: head, thorax, abdomen, sclerites, compound eyes, ocelli, antennae, labrum, mandible, hypopharynx,
labium, labial palp, maxillae, maxillary palp, prothorax, mesothorax, metathorax, legs, wings, spiracles, forewings,
hindwings, coxa, trochanter, femur, tibia, tarsus, claws, arolium, tympanum, cercus, ovipositor (females).
SKETCH
2. Similar to what you did with your crayfish, remove the following mouthparts from your grasshopper and place and tape
them INTO THE SPACE BELOW. Label each mouthpart: labrum, mandible, hypopharynx, labium, labial palp, maxillae,
maxillary palp
*** NOTE: some parts may be removed together, so BE CAREFUL!!!
Analysis
1. Fill in the following classification scheme for the Lubber Grasshopper.
Level of Classification
Kingdom
Phylum
Class
Order
Family
Genus
Species
Lubber Grasshopper
2. Is the grasshopper segmented throughout OR is segmentation more easily seen in certain regions of the body? EXPLAIN!!!
3. The grasshopper has both forewings and hindwings. Which appear to be more suited for flight? Why? Also, what do you
feel would be the function of the “other” set of wings?
4. You will notice that the wings of many insects is covered in small veins. What do you think entomologists might use these
veins for?
5. Grasshoppers have the characteristic 3 pairs of legs. Which pair seems to be more specialized? What is this pair specialized
for?
6. Go online and make observations of a “honey bee”. Make comparisons of the head, thorax and abdomen of this insect to the
Grasshopper you observed in lab. Think about the differences you notice about mouthparts, wings, legs, etc. Be sure to
discuss how these specialized body parts you notice in the honey bee might be used.
Insect
Grasshopper
Honey Bee
Head
Thorax
Abdomen
7. There are MANY different orders used to classify insects. Below, you will need to fill in the table using many different
ONLINE resources and/or your TEXTBOOK.
Insect Order
Lepidoptera
Diptera
Hymenoptera
Odonata
Isoptera
Hemiptera
Siphonaptera
Dermaptera
Orthoptera
Coleoptera
Blattodea
Phasmatodea
Mantodea
Identifying Characteristic/s
Example/s of this order