Biology 3B Laboratory Invertebrates II: Annelida, Nematoda ...

pair of membranous wings which are extension of the respiratory system. The legs are
jointed.
• Examine the wings of a beetle (Orthoptera). The forewing is called the elytra
which functions to protect the membranous hindwing that’s used for flight.
• Examine the wings of a cranefly (Diptera). The forewing is for flight and the
hindwing is reduced and modified for balance.
o ABDOMEN: The abdomen is simple, devoid of appendages, and made up of 10 to 11
segments. Note the terminal structures and use them to determine the sex of the specimen.
Be sure to compare your grasshopper to one of the opposite sex. In the female, the
ovipositor is for laying the eggs inside the earth. At the tip look for a pair of sensory
structures known as cerci.
• Observe the female cricket and notice the long ovipositor for depositing eggs.
o On either side of the first abdominal segment you might see a thin membrane, called the
tympanum - a hearing organ. Spiracles are present on either side of most of the segments.
The spiracles are most prominent in the thorax region. They are the breathing pores of the
elaborate network of the tracheal system.
Figure 13: External features of a female grasshopper.
Insect have mouth parts that are adapted for the type of feeding they specialize in. There are four
basic mouth parts: sucking mouthparts, sponging/lapping mouthparts, siphoning and
chewing/biting mouthparts. You want to be able to differentiate these mouthparts for they type of
feeding (figure 14).
o Examine the slide of the mosquito head (sucking mouthpart)
o Examine the slide of the butterfly head (siphoning mouthpart)
o Examine the slide of the fly head (lapping mouthpart)
o Examine the slide of the honeybee (chewing)
Biology 3B Laboratory Invertebrates II Page 12 of 17