L3 Thorax Flashcards
What is the pronotum
Extension of prothoracic segment, protective of dorsal surface. Can be hugely enlarged eg in Southwestern Hercules beetle, Dynastes granti
What 3 segments make the thorax?
Prothorax
Mesothrax
Metathorax
Describe the legs on each segment
each segment has a pair of jointed legs legs have 6 segments 1 Coxa 2 trochanter - 'knee' 3 femur 4 Tibia 5 Tarsus -'foot', 6 pseudosegments called tarsomeres. 6. pretarsus - 2/3 claws, paired lobes/pulvilli - have fine hairs to move across smooth surfaces.
Adaptation of: Mantid legs, Mole cricket legs, backswimmer legs.
Opposing spines on tibia and femur to grab prey.
Leg segments broad and flattened to help bury underground
Highly curved legs to propell it backwards through the water, bristled to extend SA.
Describe the gait of insects
Tripod gait - 3 legs attached to surface at any point
Galloping dung beetleuses a tripod gait usually when walking but to go faster will gallop.
Describe structure of wings
Bilayer of cuticle, thin and transparent with veins.
Veins contain trachea, nerves ad carry blood.
Used to communicate with main body of insect.
8 longitudinal veins, cells are areas of cuticle btw veins. Open cells are on edge of wing.
How do the wings join to the main body?
Join body at complex structure made of hard cuticular plates [sclerites]. This structure is simpler in advanced insects. Resilin protein is in this structure - flexible and elastic even at low temps. In fleas, resilin compresses and released to give them great jumping power.
Describe wing surface.
Surface covered in spines, mosquito wing fringed at edge with hairs and along veins.
Some have more elaborate spines are flattened into scales.
Lepidopteran wings coloured with pigment which is deposited as wings grow. structural colour from irridescence, due to microtracheae on surface of wing scales.
Describe some order’s wing protection
Dragonfly - v primitive, cant fold wings, vulnerable.
Grasshoppers - evolved ability to fold wings, and thickened, leathery forewing [protective sheath]
Coleptera - fully hardened forewing [Elytra] so able to burrow into tight places without damaging hindwings, increases niches. Elytra have no function in flight.
How to wings fold?
No muscles in wings so use muscular pumps at the base of wing to pump blood through veins to unfold wings.
Lines of flexion on wing where it folds, and can have characteristic internal or external folds
apterygota
pterygota?
wingless/ winged
Why would some insects be secondarily wingless?
if parasitic eg fleas, mites - wings would increase chance of getting pulled out
Lipoptera cervi - horse parasite, loses wings once finds host
Some lose wings after mating, as wings may only be useful for dispersal
Dragonfly vs diptera wing modifications for flight
odonata - many veins and small cells between veins. V rigid
diptera - loss of veins so more flexible and can twist in the air. Many lobes at base of wing, perhaps for channeling air smoothly over wing.
Why is increasing efficiency of flight important and how?
v. metabolically expensive
eg hairs and spines keep air flat on the surface of the wing.
Wing coupling - disturbed air rolls off forewing onto hindwing, making flight inefficient. coupling by hooks and grooves allows wings to beat as a single structure to smooth airflow.
Describe diptera hindwing
reduced to form a haltere
Clublike, many nerves and receptors at base.
Knob at end detects body movement, is heavy and as body twists, creates strain which is detected by receptors at base.
