Phylum Arthopoda - Arthropods
includes spiders,
spiders scorpions,
scorpions horseshoe crabs,
crabs
centipedes, crustaceans, insects
The largest and most diverse animal phylum.
Class Insecta - Insects
Largest group of organisms on earth - with great diversity
Especially numerous in the tropics
Insect Development
Insects have internal fertilization.
Most insects hatch from laid eggs - rarely develop within mother
After hatching young insects undergo regular ecdysis or molting
(shedding of exoskeleton) through a series of developmental stages
called instars
Often the larva is very different from the adult and undergoes
metamorphosis to become adult
In simple metamorphosis, also called incomplete
metamorphosis, there is a gradual transformation from egg, to
nymph, to adult. Immature stages are called “nymphs”
The mature adult often has wings and there is no further molting.
Nymphs normally do not have wings.
Seen in beetles, grasshoppers, dragonflies, cockroaches, silverfish
In complete metamorphosis, wings develop during a resting
stage just prior to final molt
resting stage called a pupa or chrysalis - at this time cellular
reorganization occurs to form adult body
Pupa does not normally move, except in mosquitoes
Complete
Metamorphosis
Juveniles and adults often live in distinct habitats larvae often worm-like,
worm like lacking large eyes,
eyes and legs
Larvae usually have chewing mouth-parts, even if adults have
sucking mouth-parts
Pupae are usually inactive and do not feed
seen in moths, butterflies, beetles, bees, wasps, ants, flies, fleas