Insect Anatomy part 2 Flashcards
what is the thorax
the second segement of three which makes up the tagmata of an insect and is usually divided up into three segments which have appendages
what are the three sections that the thorax or mesosoma is divided into
1) prothorax = pair of legs
2)mesothorax= pair of legs and wings
3) metathorax = pair of legs and wings
what are insect sclerites
a series of integumental plates connected by tough, elastic membrane= these plates have names
1) top dorsal = Nota
2) Bottom plates = sterna
3) side plates = pleura
what are the different segments of insect sclerites
Nota = upper, concave plates
pleura = lateral, convex plates
sterna = ventral sclerites
outline legs in insects
six jointed appendages with a multitude of functions
outline insect leg structure
- 3 pairs of walking legs= one pair per thoratic segment
- typically six-segmented
outline the different leg segemnts which make up leg structure
1) coxa
2) trochanter = two segment trochanter (only one muscled) occurs in Odonata and some hymenoptera
3) femur
4) tibia
5) tarsus = subdivided and typically a two clawed prtarsus
6)pretarsus
outline the coxa
- most basal aspect of the insec leg
- articulates with sternites
- joint between coxa and body wall may be monocondylic, dicondyic or more complicated
- may articulate with any of of the several small sclerites, pleura and or the sternum
outline the trochanter segement of the leg
- usually small
- a joint between coxa and femur
- joint between coxa and trochanter is always a dicondylic joint
- motion restricted to a forward and backward direction (vertical plane)
- appearance of two trochanters in odonata
outline the femur part of the leg
- usually long and stouter than other segments
- contains main muscles used in running, jumping and digging
- joint between trochanter and femur is usually fairly firmly attached or with only small amount of movement
outline the tibia part of the leg
- usually long and offers extra flexibility
- may carry spurs for defence
- joint between femur and tibiai is dicondylic
- head often bent so shank can flex against femur
outline the tarsus segement of the leg
- foot or contact surface of leg
- most insects it is subdivided from 2-5 tarsomeres
- tarsomeres = not true segments as lack individual musculature
- basal segment (basitarsus) has monocondylic articulation with tibia
- rest of joints lack true articulatory structures= freely moveable in membraneous joints
outline the pretarsus segment of the leg
- generally consists of a median lobe (arolium) and a pair or tarsal claws (ungues)
- diptera usually have no arolium but have membranous pulvilli , ungues and a middle empodium
what is a ariolium
found on the pretarsus section of the leg
median lobe may be membranous or partly sclerotised
= acts using suction from large numbers of minute tubular hairs enabling insects to hold onto smooth substrates
= none in diptera exepct in crane flies
what is an ungues
found on the pretarsus part of the leg and is used to assit the insect in holding substrate or prey
what is a pulvilli
found on the pretarsus section of the leg in diptera
= two pads beneath the claws often covered with fine setae to aid attachment to surfaces
what are empodia
found on the pretarsus section of the leg in diptera and are spine or lobe-like processes arising from unguitractor
what are the different leg adaptations
1) Natatorial = adapted for swimming e.g. water beetles
2) Fossorial = adapted for digging in soil e.g. mole cricket
3) Cursorial = adapted for running e.g. cockroaches
4 )Raptorial = grasping, stabbing forelegs armed with lethal spined for cathcing and holding prey = preying mantis
5) Saltatorial = large, muscular hind legs adapted for jumping e.g grasshoppers, fleas
what is meant by the terms pollen brushes and corbiculas
PB= females of bee spp collect pollen on hind tibia and basitarsi which is often enlarged and covered in dense hair
C= femal of social bumblebee spp have this aka pollen basket= smooth shiny area surrounded by ring of long hair on hind tibia
what are wings
adult outgrowths of insect exoskeletons which enable them to fly
- supported by series of sclerotised veins
- small wings buds visable on exoskeleton of hemimetaboloys insect larvae
how can wings be adapted for different spp
in small insects veins may be absent or consist only of central midrib
- increase or decrease venation network
- wing folding
- use of colour
what is meant by secondary wing loss
- wings may be present in one sex (usually male)
- selectivley lost in ‘workers’ of social insects
- wings may be produced only at certain times in life cycle
- structure and colouration will often vary with morphs
outline what happens when wings are at rest
- wings may be held flat or folded a number of times along specific patterns
- complex folding in some groups
- typically hindwings folded
- evolution of insect wings not well understood
what are the three theories of the evolution/origin of wings
1) developed from paranotal lobes, extentions of the thoratic terga, orginially acting as parachites
2)wings derived from tracheated gills or gill covers
3) from inner (endite) or outer (exite) leg segments close to the body = fossil and molecular evidence for this theory
outline wing venation
characteristic netwrok usually throughout wing tissues
- extentions of the circulatory syste,
- filled with haemolymph and conatain tracheal tubes and nerves
= in membraneous wings the viens provide strength and reinforcemnt during flight
= can be used for taxonomuc indentification
what are the different wing functions
1) communication
2) camoflague
3) thermoregulation
4) protection
5) Balance
6) flight
outline how wings can be used in communciation
- bright colours, including UV and wing patterns provide a means of inter/intraspecific communication
outline how wings are used for camouflage
crypsis allows the insect to hide from predators or helps suprise prey
outline how wings can be used for thermoregulation
- different colours reflect/absrob different wavelnegths of light
e.g. black patches on wing of some alpine butterflies help absorb solar radiation
= thermoregulate by changing wing posture
outline how wings can be used for protection
- modified hardend forewing of coleoptera
- protect hindwing which used for flying
- modified leathery forewing of orthoptera, dermaptera, mantodea, phasmatodea = tegminia
outline how wings can be used for balance
- hind wing of diptera modfied into halteres which vary in size and concerned with stability in flight
- basal lobes of halteres have companiform sensiila
outline direct and indirect flight muscles
direct = wing muscles insert direclty at wing bases which are hinged
- small movement of wing base downward lifts wing up
indirect = muscles attached to throax and flight powered by force of muscle contraction and distortion of thorax
- dorsal longitudinal muscles compress thorax causing dorsal surface of throax to bow up making wings flip down
- tergosternal muscles pull notum down again causing wings to flip up
what is meant by synchronous and asynchronous contraction
refers to ratio of muscle contraction relative to nervous innervation affecting wing beat and wing beat frequency
s= 1:1 relationship between impulses and contraction used for wing frequencies up to 100Hz
A= allows for more rapid contraction and higher wing beats over 500 HZ
= present in more advanced groups of insects
what is meant by monocondylic and dicondylic joints
mono= one point of articulation between joints allowing movement across two planes= similar to shoulder joint
di = two points or articulation allowing movement only across one plane e.g. elbow joint - limits overall movement
