1) Long evolutionary history (540+ My) 2) broad size range/habitat utilization 3) metameric body plan/rigid exoskeleton 4) profound influence of homeotic genes (read pp. 115-116) 5) co-evolution with plants/algae 6) evolution of flight Insect Diversity 29 orders total o 4 wingless (apterygotes) - examples: bristletails, springtails o 16 hemimetabolous winged (exopterygotes) (incomplete metamorphosis) examples: mayflies, dragonflies, grasshoppers, stick insects, earwigs, roaches, termites, true bugs o 9 holometabolous winged (endopterygotes) (complete metamorphosis) examples: lacewings, fleas, beetles, flies, butterflies and moths, caddis flies, ants bees and wasps Most insect species are holometabolous Could have something to do with mixed life cycle: offspring are ecologically different from adults Most insect biomass is from ants and termites: Each represents about 10% of all animal biomass Insect Anatomy (Head Thorax Abdomen) Head bears eyes (usually compound), antennae, mouthparts Mouthparts chewing (grasshoppers), sucking with stylet (bugs & aphids), sucking with coiled tongue (butterflies), etc. Antennae used to detect odors or as tactile organs Thorax 3 segments, with 3 prs. legs, winged insects normally have 2 pairs of wings Legs 6 legs (Hexapoda) Each thoracic segment supports 1 pr. Legs are segmented Last segment often bears small claw Some have legs specialized for jumping Wings probably arose once in common ancestor Most insects have two pairs Flies have 1 pr. (front pr. modified as halteres) Most membranous some leathery or hard Sometimes wings bear hairs or scales Abdomen 11 segments Bears external genitalia (e.g., ovipositor) Gas Exchange Insect cuticle highly resistant to 
(Each thoracic segment; supports; 1 pr) (Most; membranous; ) Context(Most membranous,List([1530, 1545))):(Most insects; have; two pairs Flies have 1 pr. (front pr. modified as halteres) Context(Most insects have Most membranous,List([1452, 1545))):(two pairs Flies; have; 1 pr) Context(Most membranous,List([1530, 1545))):(winged insects; normally have; 2 pairs of wings Legs 6 legs (Hexapoda) Each thoracic segment supports 1 pr) Context(winged insects normally have Most membranous,List([1207, 1545))):(Each; represents; about 10% of all animal biomass Insect Anatomy) Context(Each represents winged insects normally have Most membranous,List([858, 1545))):(ants bees and wasps; Could have; ) Context(ants bees and wasps Could have Each represents winged insects normally have Most membranous,List([653, 1545))):(something to do with mixed life cycle; are; ecologically different from adults) Context(ants bees and wasps Could have something to do with mixed life cycle are Each represents winged insects normally have Most membranous,List([653, 1545))):(springtails; o; 16 hemimetabolous winged (exopterygotes) (incomplete metamorphosis) examples) Context(ants bees and wasps Could have something to do with mixed life cycle are Each represents winged insects normally have Most membranous,List([653, 1545))):(Most insect species; are; holometabolous) Context(Each represents winged insects normally have Most membranous,List([858, 1545))):(Most insect biomass; is; from ants and termites) (Legs 6 legs; Some modified; as halteres) (Legs; are segmented; ) (antennae; sucking; with stylet) (Antennae; to detect; odors) (Last segment; bears; small claw; T:often) (mouthparts Mouthparts; chewing; grasshoppers) (legs; specialized; ) (wings; bear; T:Sometimes) (caddis; flies; )
Most membranous,List([1530, 1545)) Most insects have Most membranous,List([1452, 1545)) Most membranous,List([1530, 1545)) winged insects normally have Most membranous,List([1207, 1545)) Each represents winged insects normally have Most membranous,List([858, 1545)) ants bees and wasps Could have Each represents winged insects normally have Most membranous,List([653, 1545)) ants bees and wasps Could have something to do with mixed life cycle are Each represents winged insects normally have Most membranous,List([653, 1545)) ants bees and wasps Could have something to do with mixed life cycle are Each represents winged insects normally have Most membranous,List([653, 1545)) Each represents winged insects normally have Most membranous,List([858, 1545))
Each thoracic segment Most Most insects two pairs Flies winged insects Each ants bees and wasps something to do with mixed life cycle springtails Most insect species Most insect biomass Legs 6 legs Legs antennae Antennae Last segment mouthparts Mouthparts legs wings caddis
supports membranous have have normally have represents Could have are o are is Some modified are segmented sucking to detect bears chewing specialized bear flies
1 pr
two pairs Flies have 1 pr. (front pr. modified as halteres
1 pr
2 pairs of wings Legs 6 legs (Hexapoda) Each thoracic segment supports 1 pr
about 10% of all animal biomass Insect Anatomy
ecologically different from adults
16 hemimetabolous winged (exopterygotes) (incomplete metamorphosis) examples
holometabolous
from ants and termites
as halteres
with stylet
odors
small claw T:often
grasshoppers
T:Sometimes