THORAX
- major sclerites: tergum (notum), pleuron, sternum.
- number of segments - three.
i. prothorax, mesothorax, metathorax
ii. all have legs. Sketch
iii. two pairs of wings in many adult insects.
exceptions:
a) "primitive"
insects. (Apterygotes = without wings).
b) Diptera (true flies), (first pair wings; second pair = halteres).
c) secondarily wingless.
e.g. some female moths.
d) Coleoptera (beetles)
highly modified forewings = elytra
heavily sclerotised - protection; some may
be fused).
Wings - transverse section
SKETCH
- living tissue.
label parts: cuticle, epidermis, trachea, nerve, blood space with haemocytes "blood cells" (this space is continuous with haemocoel).
Mesothoracic Segment see HANDOUT
1. membranous wing attachment.
2. axillary sclerites - minor adjustments in wing position.
- and/or transmits movements
of thorax to wing.
3. pleural wing process-
"fulcrum".
4. basalar and subalar sclerites - involved in wing movements.
- some direct muscles attach.
5. various sutures.
6. pre- and postalar arms - bridge/connect tergum with pleuron.
7. pleural suture - internally apodeme (pleural apophysis)
8. coxal cavity - coxa arises from "side" of body not
bottom(sternum).
9. trochantin - second articulation process.
- first is condyle extension of the pleuron.
= dicondylic attachment - limits range of motion.
11. furcal pit - external marker for the furca.
Wing base with axillary sclerites. see HANDOUT
- these sclerites transmit movements of the thoraxproduced by the flight muscles to the wing.
- each sclerite articulates with different vein(s) in the wing.
-these sclerites and their attached muscles are also used during flight to change wing shape.
-in some insects these sclerites aid in wing folding when at rest..
Legs
- each of the three thoracic segments also bear a pair of legs.
- parts (articles or segments) making up the leg are;
coxa, trochanter, femur, tibia and tarsus and pretarsus.
SKETCH
- note especially the location of the coxa - this segment does not extend from the underside of the insect but more from the side. Why is this important?
- in many insect species these are used for walking but in others have become modified and specialized for jumping, swimming and digging.
"Internal" Skeleton
apodemes/apophysis
head - tentorium , marked by tentorial pits (on external exoskeleton).
- strengthens the exoskeleton of the head.
- helps protect the brain.thorax - phragma internal projection of the notum. SKETCH
- pleural apophysis - marked by the pleural sulcus.
- furca - marked by furcal pits and sulcus.- attachment of muscles.
- adds rigidity to thorax - why is this important?
abdomen - minimal.