b) 3 tagmata:

• head- 1 pair antennae + up to 4 pair thoracic-like legs, compound eyes
• thorax- variable number of segments with similar biramous limbs
• abdomen (=pygidium)- variable number of fused abdominal segments

b) SuperCl. MYRIAPODA: (>13,000 terrestrial spp; 1 mm - 30 cm)

- body has 2 tagmata (head, trunk); the trunk has many similar legs
- compound eyes are lost (except some centipedes)

- Cl. CHILOPODA (centipedes, ~2,800 spp.) 15 - 177 pairs of legs; 1st pair bears poison claws; mostly predatory
- Cl. DIPLOPODA (millipedes, ~8,000 spp.): 100 - 700 pairs of legs; adjacent trunk segments fuse yielding 2 pairs of legs per body unit (diplosegment); mostly herbivores

c) SuperCl. HEXAPODA (the insects; >1,100,000 described spp.):

- body has 3 tagmata (head, thorax, abdomen); thorax bears 3 pairs of walking legs; abdomen lacks limbs
- typically have 1 pr compound eyes and 3 medial ocelli (simple eyes)
- extremely successful group, but curiously never invaded the sea

- APTERYGOTA: 4 classes; lack wings; ametabolous (gradual) development; internalized mouthparts (entognathus)
- Cl. PTERYGOTA: the winged insects; external mouthparts (ectognathus)

- SubCl. EXOPTERYGOTA: wing buds are external; mostly hemimetabolous development (nymphs resemble adults but lack wings)
- SubCl. ENDOPTERYGOTA: wing buds arise from internal imaginal discs; holometabolous development (larvae differ from adults; radical metamorphosis takes place in a pupal stage; emerge as fully formed adult)

d) Ommatidium form (4-part crystalline style in Crustacea + Hexapoda but not Myriapoda) raises doubts about 'uniramian' monophyly