The Thorax - Insect Anatomy

What are the 3 segments of the thorax?

Prothorax

Mesothorax

Metathorax

Which two segments have wings in pterygote adults?

Pterothorax: meso and metathorax

What is the main function of the prothorax?

Head movement and front leg

What was the prothorax modified into?

The neck region

The anterior portion of the prothorax is ______

Membranous with 1 or 2 cervical sclerites

True or False: reduced prothorax is common in strongly flying insects

True

True or False: spiracles are present in the prothorax

False, only meso and metathorax

What is greatly modified for flight?

The pterothorax

True or False: segments in pterothorax telescope

False

How is the pterothorax modified for flying ability?

Sclerotized pleuron

Many extra strengthening ridges

Membranouse regions greatly reduced (a rigid structure)

Segments don’t telescope

Which segment is greatly expanded for flying?

Mesothorax

List parts of the pterothoracic notum (7-8)

Prescutum

Scutum

Scutellum

Alinotum

Postnotum (postscutellum)

Anterior and posterior notal wing processes

Sometimes reversed notal suture

What is the main part of the pterothoracic notum?

Scutum

What is separated from the scutum by scutoscutellar suture (v-shaped)

Scutellum

What is separated from the scutum by transverse or prescutal suture?

Prescutum

What is the functional plate? What are the parts it is made up of?

Alinotum = scutellum + scutum + anterior acrotergite

What part of the pterothoracic notum was modified to articulate with the wing? What are the 2 parts it includes?

Lateral margin

Anterior and posterior notal wing processes

What axillary sclerites of the wings does the anterior and posterior notal wing processes articulate with?

1st and 3rd axillary sclerites

What is phragmata?

Enlarged antecostae

Point of attachmenet for longitudinal muscles that pull on the phragmata to bow tergum upward (causes downstroke of insect flight)

What region is usually entirely membranous?

Pterothoracic pleuron

Where does pleural sclerites derive from in the pterothoracic pleuron?

The subcoxa

What are the 3 sclerites from subcoxa?

Anapleurite (dorsal)

Coxapleurite or trochantin (articulating with coxa)

Sternopleurite (usually fused with sternum)

True or False: the pleural sulcus is in all insects with wings

True

List 5 parts that are part of pleural sulcus

Episternum (anterior)

Epimeron (posterior)

Pleural wing process (fulcrum of wing)

Epipleurites = Basalare + Subalare

What is the pleural sulcus internally represented by?

The pleural ridge

Pleural apophyses - extends from coxa to pleural wing process

What extends from the coxa to the pleural wing processes?

Pleural apophyses

Where is the pleural apophysis conneced to?

Sternal apophysis

The portion of coxa embedded in the body wall is called _____ in diptera and mecoptera

Meron

How is the pleural sulcus further divided?

Anepisternum and katepisternum

Anepimeron and katepimeron

The ____ is the anterior subdivision of episternum

Preepisternum (or prepectus in hymenoptera)

The definitive sternal plate is called ______

Eusternum

How is eusternum divided?

Divided by sternacostal suture into anterior basisternum and posterior sternellum

What are the 6 parts of the eusternum?

Presternum

Basisternum

Sternellum

Sternal apophyseal pit

Sternacostal suture

Intersternite

What is on the intersternite?

Spinal pits (=spinasternum)

What are apophyses?

Large internal structures for muscle attachment and structural stability

What fuses with eusternum?

The sternopleurite of the subcoxa

What do the internal ridges do for the thoracic endoskeleton?

Allow for muscle attachment

Provide rigid structure

What is the inside fold of the pleural sulcus?

Pleural ridge

What are 3 internal ridges in the thoracic endoskeleton

Pleural ridge

Scutoscutellar ridge

Sternacostal ridge

What are the size of apodemes and their association?

Small

Associated with single muscles

What are the size of apophyses and their association?

Large

Associated with external pits

Name two apophyses

Pleural and sternal apophyses

What are apophyses for?

Muscle attachment and structural support

How are apophyses attached?

Attached by musculus latus, resilin, or fused (fused is most common)

What does the thoracic endoskeleton include?

Internal ridges, apodemes and pophyses, and spinal pit

What is the furca? What does it do?

Longitudinal infolding of sternum formed by median longitudinal invagination of sternum

Strengthens sternum

What is the furca externally?

Vental longitudinal groove

Sternum infolded