50 TO 60 PERCENT OF INSECTS ARE HERBIVORES INSECTS HAVE HAD A LONG EVOLUTIONARY HISTORY WITH PLANTS (SOME 50 MILLION YEARS) EVEN SO, HERBIVORY IS FOUND IN ONLY 9 OF THE 27-30 ORDERS OF INSECTS WHY?

LITTLE DAMAGE SEEN ON PLANTS

PROBLEMS IN BECOMING A HERBIVORE 1. ARIDITY 2. REMAINING ON PLANT 3. READILY VISIBLE TO ENEMIES 4. POOR NUTRIENT QUALITY 3. PLANT DEFENSES STRUCTURAL CHEMICAL

ALL PLANT PARTS UTILIZED HERBIVORE LOAD INCLUDES GENERALISTS AND SPECIALISTS MONOPHAGOUS, OLIGOPHAGOUS, POLYPHAGOUS DEFOLIATORS VS. SAP SUCKERS HERBIVORE LOAD CAN BE HEAVY CLOVER – 200 SPP., CORN – 300 SPP., APPLES – 400 SPP., OAKS – 1500 SPP.,

INVASIVE SPECIES ESCAPE ENEMIES AND ARE POORLY ATTACKED MANY INTRODUCED SPECIES HAVE BECOME IMPORTANT WEEDS CANADIAN THISTLE GARLIC MUSTARD GOATWEED WATER HYACINTH COMMON RAGWEED (IN RUSSIA) SPOTTED KNAPWEED MANY OF THESE ARE SUBJECTS OF BIOLOGICAL CONTROL

FEEDING HABITS 1. CHEWING INSECTS 3. GALL-MAKING INSECTS DEFOLIATORS, SKELETONIZERS, MINERS LEAF TIERS AND LEAF ROLLERS BORERS 2. SUCKING INSECTS XYLEM VS PHLOEM FEEDERS 3. GALL-MAKING INSECTS VAST ARRAY OF SPECIES, WITH SOME 800 SPP. ON OAKS ALONE

PLANTS ARE NUTRIENT POOR 1. PLANT TISSUE LARGELY COMPOSED OF WATER AND RELATIVELY UNDIGESTIBLE COMPOUNDS 2. THIS POOR NUTRIENT STATE IS COMPENSATED FOR BY THE ABUNDANCE OF PLANTS 3. SEEDS AND POLLEN ARE MUCH MORE NUTRITIOUS 4. ACTIVE MERISTEM IS HIGH IN PROTEIN

HOST PLANT SELECTION MANY HYPOTHESES NUTRIENT SCHOOL VS. SECONDARY PLANT SUBSTANCES SCHOOL CLUES UTILIZED BY INSECTS TO FIND CORRECT HOST SIZE, SHAPE, AND COLOR TEXTURE NUTRIENT STATE PRESENCE OF ATTRACTANTS AND REPELLENTS

THE NUTRIENT SCHOOL HOST SELECTION BASED ON PRESENCE OR ABSENCE OF PROPER NUTRIENTS IN CORRECT PROPORTIONS ASSUMES THAT INSECTS CAN DETECT NUTRIENTS AND THEIR CONCENTRATIONS IN PLANTS NO LONGER ACCEPTED

THE SECONDARY PLANT SUBSTANCES SCHOOL HOST SELECTION BASED ON INSECT’S ABILITY DETECT TO DETECT ATTRACTANTS AND REPELLENTS INSECTS USES GUSTATION AND OLFACTION SECONDARY PLANT SUBSTANCES APPARENTLY PLAY NO ROLE IN PLANT METABOLISM, BUT PLAY IMPORTANT ECOLOGICAL ROLES

SOME IMPORTANT CHEMICALS (SEVERAL THOUSAND KNOWN) GLUCOSIDES ALKALOIDS PHENOLIC COMPOUNDS TERPENES TANNINS SAPONINS PYRETHRUMS HORMONES

CYANOGLYCOSIDES IN WILD BLACK CHERRY 1. SERVES AS ATTRACTANTS FOR TENT CATERPILLERS 2. SERVES AS REPELLENTS FOR MANY OTHER INSECTS 3. CYANIDE CONCENTRATION HIGH ENOUGH TO KILL CATTLE IF THEY EAT DAMAGED LEAVES

WILD BLACK CHERRY (PRUNUS SEROTINA)

TENT OF TENT CATERPILLAR