Insect Biology February 4, 2008

Development Ametabolous Development Hemimetabolous Development Holometabolous Development

Abdomen 9-11 segments Dorsal tergum, ventral sternum 8 segments with spiracles Genitalia, cerci

Digestive System Alimentary canal Water+food--enzymes-->absorbable molecules+energy+wastes

Circulatory System Open Hemolymph 5-40% of body weight Hemocoel--body cavity Dorsal vessel

Respiratory System Insects need oxygen Spiracles, trachea

Holometabolous Big change from larva to adult Wings develop internally Undergo pupal stage to form adult Pupa: non-feeding, generally immobile intermediate stage between larvae and adult

All insects start as eggs Wide variety of forms Eggs

Larval/Nymph Stages Ametabolous/hemimetabolous young: nymphs Nymph: immature insect with external wingpads Naiad: immature insect with external wingpads and gills Holometabolous young: larvae Larva: immature insect with internally-developing wingpads

Larval Stages Instars 4-6

3 PAIRS LEGS, WELL DEVELOPED HEAD, CHEWING MOUTHPARTS ABDOMINAL PROLEGS, SCLEROTIZED HEAD, CHEWING MOUTHPARTS LACK ALL TRUNK APPENDAGES, HEAD CAPSULE VARIES ADAPTED FOR MINING IN SOIL, MUD, ANIMAL OR PLANT TISSUES

Pupa Erroneously called “resting stage” Breakdown/buildup of body Can last a long time--dies when runs out of energy Used to survive harsh conditions

When sexually mature Imago (Adult)

Ametabolous Orders Thysanura Thysan-fringed -ura tail Mandibulate mouthparts Three caudal appendages Long segmented antennae Common members: Silverfish, firebrats

Hemimetabolous Orders Blattodea From Latin for “cockroach” Broad body Head tucked far under thorax Wings (if present) lie flat, overlapping in abdomen

Dermaptera Derm--skin, -ptera--wings Chewing mouthparts 2 pairs wings, may be very short Cerci at tip of abdomen Feed mostly on dead vegetation can attack green leaves and fruit, small insects Found near carrion--probably eating maggots Pincer bugs, earwigs

Isoptera Iso--equal, ptera--wings Termites Chewing mouthparts Caste system--workers, soldiers, two or more types of reproductives Workers very pale, soldiers have big heads Primary reproductives--wings, 60-80 eggs 2 yrs Secondary reproductives within colony, wing pads, 60-80 eggs per day

Hemiptera Hemi--half, -ptera--wings True bugs Sucking mouthparts arising in front of middle of ventral surface of head Hemelytra Bedbugs, kissing bugs

Holometabolous Orders Lepidoptera Lepid-scaly, -ptera--wings Larvae (caterpillars) have chewing mouthparts Adults have siphoning Pupae either naked or encased in silken cocoon