1. 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 ORDERS OF INSECTS
WHY?

2. LITTLE DAMAGE SEEN ON PLANTS

4. 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

5. 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.,

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

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

13. 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

14. WILD BLACK CHERRY (PRUNUS SEROTINA)

15. TENT OF TENT CATERPILLAR