Download Biology 455 – Entomology Lab Insect Anatomy

Biology 455 – Entomology Lab
Insect Anatomy
During this lab, you will explore the external and internal anatomy of a cricket. This lab is
intended to familiarize you with the general morphology of insects, and to introduce you to the
vocabulary of insect “parts”. You will need to know and use this stuff as you identify and study
various specimens throughout the course. You are expected to know the underlined terms, and to
be able to identify the corresponding body parts on an insect specimen.
The lab is self-paced. Work through the handout, making sure that you can find and identify each
of the body parts listed, and that you can answer any questions. Pertinent diagrams are included
to help you, but you should also make your own sketches and notes.
I. External Anatomy
• Examine your cricket and identify the 3 main body regions: head, thorax, and abdomen.
A. Head
• An insects head is connected to the thorax by the flexible cervix (neck).
• Locate the cervical sclerites on the cervix. (A sclerite is a hardened plate on an insect’s
exoskeleton)
Head structures:
• Locate the epicranial suture that divides the head into two parietal areas. The frons is bound
by the antennae. The gena is the “cheek” region below the eye. It is separated from the frons
by the genal suture. The clypeus lies below the frons. The labrum is attached to the lower
border of the clypeus and forms the anterior cover of the buccal cavity. The sclerites at the
posterior end of the head form the occiput.
• On the antennae, distinguish the scape, pedicel, and flagellum.
• The compound eye is composed of ommatidial facets.
• Locate the median and lateral ocelli.
Mouthparts:
• Detach and examine the series of mouthparts, working from anterior to posterior. Consider
the structure and function of each part carefully.
• Mandibles: detach and examine the mandibles. Are they symmetric?
• Maxillae: Locate cardo, stipes, lacinia, galea, and maxillary palps.
• Labium: This forms the posterior closure of the buccal cavity. Locate the postmentum,
prementum, ligula (=glossae and paraglossae), and labial palps.
• Hypopharynx: this is the “tongue” on the anterior surface of the labium.
B. Thorax
• Distinguish the prothorax, mesothorax, and metathorax.
• Locate the dorsal nota (tergum). Locate the pleuron and the pleural suture that separates the
episternum and epimeron. On the ventral side, locate the sternellum. Locate the thoracic
spiracles.
Wings:
• With what body segments are the wings associated?
• What do you think are some of the functional distinctions of front and hind wings?
•
Locate the axillary sclerites. We will examine wing structure and morphology in more detail
later.
Legs:
• The proximal segment of a leg is the coxa. The trochanter articulates with the coxa, and is
fixed to the femur. The femur is connected to the tibia, which in turn is connected to a series
of segments called the tarsus. At the distal end of the tarsus is the pretarsus. The pretarsus
includes a pair of tarsal claws and a pulvillus.
• How many tarsal segments does a cricket have?
C. Abdomen
• There are 11 abdominal segments. How many of them can you distinguish?
• The anterior 7 are always distinct. Identify the tergum, sternum, pleuron, and spiracles on
each.
• The posterior 4 segments are variously modified and carry the genitalia and cerci. Locate the
epiproct, paraprocts, cerci, anus, and genital aperture.
• Is your cricket male of female? How do you distinguish the sexes?
II. Internal anatomy
To examine the internal anatomy, you will have to dissect a cricket. Anesthetize a cricket with
CO2 or cool it on ice. Place the cricket in a dissecting dish and pin it as demonstrated. Carefully
remove the wings. Cover the cricket with saline, and cut it open along the midline, posterior to
anterior.
•
•
Locate the silvery, air-filled tracheal tubes and air sacs. Trace them to the spiracles.
Locate the fat body.
Gonads and accessory glands:
• In a female cricket, locate the ovaries and identify the ovarioles. Locate the oviduct and
spermatheca.
• In a male cricket, locate the testes and seminal vesicles. Locate the mushroom gland,
ejaculatory duct, and aedeagus (penis).
Gut:
• Identify the pharynx, esophagus, crop, and proventriculus of the foregut. Identify the gastric
caeca, ventriculus, and pylorus of the midgut. Identify the ileum (colon), rectum, and anus of
the hindgut.
• Identify the Malpighian tubules.
• Open the crop and proventriculus and examine their interior structure. What do you think the
crop and proventriculus do?
Nervous system:
• The insect nervous system is located ventrally along the body axis, and is composed of a
series of ganglia. Locate the subesophageal ganglion.
CUTICLE, CROSS SECTION
HEAD
DIGESTIVE SYSTEM
MOUTHPARTS
LEGS
REPRODUCTIVE SYSTEM
NERVOUS SYSTEM
RESPIRATORY
SYSTEM
CIRCULATORY
SYSTEM