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Grasshopper dissection EXTERNAL ANATOMY

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Grasshopper dissection EXTERNAL ANATOMY Powered By Docstoc
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                  Grasshopper Dissection DAY 1- External Anatomy

Background: Insects are a class of invertebrates that are widespread all over the earth. There are over
one million species, and perhaps many more yet to be discovered. However, with all their differences, they have
several common characteristics: a hard, outer covering called an exoskeleton, six jointed legs, and three
distinct body sections, the head, the thorax, and the abdomen. Grasshoppers are in the order Orthoptera,
which have large hind legs for jumping, mouth parts for chewing, and leathery wings. After hatching, they
undergo a gradual metamorphosis through various nymph stages before they reach adulthood.

Purpose: To locate and observe the different parts of a grasshopper.

Part 1: Observation of EXTERNAL anatomy:
The grasshopper, like all insects, has 3 distinct sections: the head, thorax, and abdomen. Observe each
of these in turn.

HEAD

   1. The jointed antennae are sensory organs of touch, taste, scent, and vibration.
   2. The two large, round compound eyes detect movement, but the grasshopper also has 3 simple
      eyes called ocelli that detect light and darkness. Two of these are located above the bases of
      the antennae, and the other are directly between the compound eyes.
   3. The mouth consists of several parts that allow the grasshopper to chew its food. First is the
      broad upper lip called the labrum. To the sides of this are two hard mandibles that work like
      a sideways jaw to crush the food. Underneath is a pair of maxillae for chewing, each with a
      feeler on the side called a maxillary palp. Finally there is the lower lip, or labium with 2 short
      labial palps.

THORAX

       1. The thorax is the middle section of the grasshopper. All six legs and both sets of wings are
          attached to it.
       2. Just behind the head is a saddle shaped shield called a pronotum.
       3. All the legs have a similar structure with a femur, tibia, and tarsus, but the hind legs are
          much larger to allow the grasshopper to leap long distances.
       4. Notice the claws at the end of the tarsus, as well as the spurs projecting from the base of
          the tibia.
       5. The front wings, called the tegmina, are tough and leathery and may have dark spots. They
          lie over the membranous hind wings to protect them. The hind wings are used for flight, but
          some grasshoppers have short, round wings are flightless as adults.
ABDOMEN



     1. The abdomen has 11 segments, the first of which is fused to the thorax.
     2. On the first segment, often hidden by a wing or leg, is the tympanum, a round flat
        membrane that acts as the grasshopper’s ear drum.
     3. The segments of the abdomen have a small opening on each side called a spiracle. These
        opening s allow air to pass through and are connected to a network of air tubes (trachea)
        inside the grasshopper. Together the spiracles and trachea function as the grasshopper’s
        respiratory system.
     4. The abdomen of the male grasshopper has a blunt end, but the females have four end
        projections called ovipositors for laying eggs.



exoskeleton

antennae

ocelli

labrum

labium

mandibles

femur, tibia, tarsus          3 parts of the leg

claws

spurs

tegmina

tympanum

spiracle

ovipositors

				
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posted:9/5/2012
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