1. Phylum Arthropoda
Class Insecta

2. Class Insecta – Characteristics
Approximately 1 million species – more than all other animals combined
Order
World
North America
Coleoptera (Beetles)
290,000
29,000
Lepidoptera (Moths, butterflies)
180,000
14,000
Hymenoptera (bees, ants, wasp)
103,000
17,500
Diptera (flies, gnats, mosquitoes)
85,000
16,000

3. Class Insecta – Characteristics
3 distinct somites
Head, thorax, abdomen
1 pair antennae
3 pair jointed legs attached to thorax – “hexapods”
2 pair of wings usually attached to thorax

4. Class Insecta – Characteristics
Mouth parts adapted for chewing, piercing, & sucking
Digestive -- complete; salivary glands & “gastric caeca” aid in digestion
3 regions: foregut, midgut, & hindgut
Circulatory – open; consists of slender, dorsal heart
Hemolymph collects in sinuses in hemocoel

5. Class Insecta – Characteristics
Respiration – Air is drawn in from sides of abdomen through “spiracles”
Trachea branches into smaller “tracheoles” where gas exchange takes place
Excretion – “Malpighian tubules” function similar to kidneys, located in anterior portion of the hindgut
Insects can have as few as 2 or as many as 100 Malpighian tubules

6. Marcello Malpighi, 1628-1694 Rest his dearly departed soul :-(

7. Class Insecta – Characteristics
Nervous system – Double ventral nerve cord
Several pairs of ganglia per segment
Well developed sense organs

8. Class Insecta – Characteristics
Sensory reception
Simple eyes (ocelli) and compound eyes
Antennae – Single pair; chemoreceptors, “tactile hairs”
Sound reception – tympanic membrane on each side of body

9. Class Insecta – Characteristics
Reproduction – Sexes separate, “dioecious”
“Viviparous”, internal fertilization with internal development.
Eggs develop with a yolk & thin protective shell
Eggs can be deposited with an “ovipositor”
Two types of development
Complete & incomplete metamorphosis

10. Complete Metamorphosis
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Complete Metamorphosis

11. Incomplete Metamorphosis
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Incomplete Metamorphosis
This stage involves a series of “molts”

12. Reasons insects are so successful…
Exoskeleton for protection
Mobility – wings and legs
Small body size
Efficient energy use
High reproductive success
Short life cycle – leads to adaptive changes
Metamorphosis is controlled by hormones

13. Reasons insects are so successful…
Protective coloration
Mimicry
Defensive chemicals