• Solid waste leaves through anus.
  • nitrogen-containing waste --> cellular metabolism removed in different ways.
  • Terestial arthropods (insects +spiders) - nitrogen-containing, using Malpighian tubules.
  • Tubules remove waste from blood, and concentrate and add undigested food before it leaves the anus.
  • small excretory glands at bases of legs in addition and instead of Malpighian tubules.
  • Aquatic - cellular waste diffuse from body into water at unarmored places such as Gills.
  • Aquatic - (lobsters) eliminate through paid of green glands located near base of antennae.
  • emptied to outside through pair of openings on head.
  • well developed nervous system
  • brain - consists of pair of ganglia in head
  • Ganglia --> central switchboards --> incoming/outgoing information and instruction of muscles.
  • Brain -->pair of nerves run --> around esophagus and connect to the brain --> nerve cord -->ventral part of body.
  • Ganglia local command center to coordinate movement of legs and wings. <-- why insects can still walk or flap wings once head is cut off.
  • body segments are fused together.
  • simple sense organs = statocysts and chemical receptors.
  • compound eyes for most, which consist of 2000 separate lens- that can see color and motion.
  • better eyesight than us <-- hard to swat flies and mosquitoes
  • eg. quick moving fan is visible to the flies eye, but to ours it's a blur.
  • crustaceans and insects have a well developed sense of taste but places in strange places. (mouth, antennae, legs)
  • detect movement in air and water.
  • well developed ears beyond us humans.
  • ear drums for grasshoppers are behind their legs.
  • scorpions/bees/ants - venomous stings/bites - spiders/centipedes.
  • lobsters/crabs = powerful pincher.
  • diversion = crab can drop claw/leg and it will keep moving to distract prey, as crab gets away. (will grow back later)
  • camouflage and mimics warning coloration (mimicry)


  • well-developed muscle; coordinate by nervous system.
  • generate by contraction --> transfer to exoskeleton.
  • body joint- positioned to flex and others to extend it.
  • pull muscles vs exoskeleton - allows to fly, walk and flap.


  • males and females - sperm and eggs - fertilization in female.
  • some crustaceans (spiders) - drop packet of sperm, ladies pick it up.
  • in other special organ used to deposit sperm inside.

Growth & Development


  • exoskeletons present problem in term of growth.
  • to grow must molt/shed.
  • controlled several important hormones. (molting hormone)
  • epidermis (layer cell cover outside of body)
  • digests inner part of exoskeleton + absorb chitin to recycle chemicals.
  • eat what is left of exoskeleton.
  • secrete new exoskeleton in old one, pulls out of old one.
  • expand + new exoskeleton (still soft) stretches.
  • new exoskeleton harden few hours --> few days.
  • Metamorphosis/dramatic change in form
  • grasshoppers/mites/crustaceans - eggs -->young animals.
  • lack sexual organs, and adult structures. like wings.
  • grow - molt - grow + molt +gain characteristic.
  • insects - bees/moths/beetles - 4 stage process. =complete metamorphosis.
  • egg - hatch into larvae (look nothing like parent)
  • certain are - shed 1 more time = Pupae.
  • body totally rearranged - grow from tiny buds.
  • structures broken down supply raw materials for adult structures.
  • complete - adult emerges with internal/external parts never had.
  • acts different too (juvenile hormone) keep insect in larval each molt.
  • Pupa, Juvenile hormone drops. pupa-to-adult molt.
  • Juvenile/molting/other hormone important.
  • possible to combat by tampering with hormones.
  • certain plants, produce chemicals to prevent molting/development at wrong rate/dysfunctional adults.
  • humans figures out chemicals to do this.