Introduction: Insects are arthropods with jointed appendages, segmented bodies, and an exoskeleton composed of chitin. Insects are in the class Insecta, & are the largest and most diverse group of animals on earth. The genus Romalea is a large grasshopper common in the southeastern United States. Insects have three body regions (head, thorax, & abdomen), 6 pairs of legs attached to the thorax, a single pair of antenna attached to the head, mouthparts adapted for chewing or sucking, and two pairs of wings. Some insects may have a single pair of wings or be wingless. 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 body 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.
Procedure (External Anatomy): Examine the entire grasshopper and identify the major subdivisions and parts of the body.
- Obtain a preserved grasshopper & rinse off any preservative with water. Place grasshopper in the dissecting pan.
- Observe that the body of the grasshopper is divided into 3 regions — the head, the thorax, and abdomen.
- Examine the head and locate the following parts:
Antennae (two, slender appendages)
Compound eyes (2, large lateral)
Ocelli (or simple eyes) – 3, small, between compound eyes
Mouth parts – Labrum (upper lip), mandibles (jaws) below the labrum, maxillae located behind the mandibles to help cut & hold food, and the lower lip or labium
|1. Labrum||5. Maxillary Palps|
|2. Mandibles||6. Maxillae|
|3. Labial Palps||7. compound eye|
|4. Labium||8. ocelli|
- Label the mouthparts, eyes, and antenna on Figure 1 in your lab.
- Using forceps, remove each of the appendages from the head, and examine them with the magnifying lenses.
Legs (first 2 pairs are for walking & the last pair are for jumping)
Wings (forewings have a leathery appearance & protect the hind wings)
- Using forceps, remove one of the walking legs and identify these parts — the coxa connects the femur (the thickest part of the leg) to the grasshopper’s body; a slender, spiny tibia connects the femur to the tarsal segments (lowest part of the leg).
- Remove a jumping leg and attach the walking leg & jumping leg to Table 1.
- Raise both pairs of wings and locate the first abdominal segment.
- Locate the tympanic membrane or eardrum on the first abdominal segment.
- Using a magnifying glass, locate the spiracles or tiny pores for respiration on each side of the abdominal segments.
- Determine if your grasshopper is a male or female by looking at the end of the abdomen. Females have a tapered abdomen that ends in a pointed egg laying tube called the ovipositor. Male have a more rounded abdomen that turns upward.
- Once you have completed identifying the parts on Table 1. Have your teacher check you off and initial your lab worksheet before you discard them.
Spiracles – small openings on the side of somites or body segments
Tympanic membrane (Auditory Organs) -two located laterally on the 1st body somite or segment
Ovipositor (on female)