Lecture 25: The Perfumes of
Sex & Life
CHEMICAL COMMUNICATION
Key Points:
Chemical communication
• What is the difference between semiochemicals
and pheromones
• Describe two modes of action of pheromones
• How can sex pheromones improve our food
quality
• Name three pheromones and how they work
• Define Intra specific and Interspecific
• How does an HIPV work
Semiochemicals
• KAIROMONES
– Inter-species specific
– Advantage to the receiver
• ALLOMONES
– Inter-species specific
– Advantage to the sender
• PHEROMONES
– Intra-specific
Pheromones
• “A chemical signal released to the outside
of the body of the producer that effects
the physiology or behavior of a
receiving individual of the same species.”
• From the Greek pherein (to carry) +
hormon (to excite)
Pheromones
• Produced from exocrine glands
– that’s EXO not ENDO
– Produced in liquid, but can be released as
– streams, droplets, thin films, aerosols
• Creation of the “Active Space”
For your interest
Pheromonal Active Space
• For some insects it can be quite large
– Gypsy Moth
– 1,800 meters (that is more than one mile)
by 100 meters
by 50 meters
• And powerful
– one GM female possesses 0.01 μg which
hypothetically could incite a response in one
billion males.
For your interest
Pheromones
• Two MODES OF ACTION
1) RELEASERS
immediate effect on the central nervous
system & behavior of the receiving animal.
2) PRIMERS
triggers a chain of physiologicaldevelopmental events that may take days,
to weeks before an overt response is seen.
Pheromones
• Classes/Types
– Sex pheromones
– Trail pheromones
– Alarm pheromones
– Aggregation pheromones
– “Social” pheromones
Sex Pheromones
• The best known & best studied of all
pheromone classes.
–
–
–
–
Function: Gender attraction
Most frequently females “calling” to males
Occasionally males “calling” to females
Rarely, sex attractants released by both
genders of a species.
Sex Pheromones
• Chemistry of sex pheromones known for
several hundred insect species.
• Uses:
– monitoring
– control
• trap out
• male confusion
Vine mealybug
a) native to the Mediterranean region
b) spreading throughout CA vineyards
VMB / vine / 2 min search
“Microencapsulated” sex pheromone
and mating disruption
5
a
Control
Sex pheromone
4
3
b
2
1
0
Anagyrus pseudococci
For your interest
Trail Pheromones
• Commonly found in numerous social
insect species
– ants, termites & some non-social aggregating
caterpillars (tent caterpillars)
– Used for orientation to & from the nest for
the establishment of foraging trails
(highways)
Trail Pheromones
• Volatile
– frequently added to when forage is
rewarding
– quickly dissipates when forage is reduced
• Sources
– tarsal glands - abdominal glands - venom
• Potential for control??
– Has been tried experimentally with pest ants
• e.g., fire ants
Alarm Pheromones
• Common in social insects & aggregate
feeders
– wasps, termites, bees, & some aphids
• Function
– defense
• recruitment of nest-mates
– dispersal
• aphids
• Volatile
Aggregation Pheromones
• Function:
– Signal that recruits conspecifics to a food
source.
– Known in bark beetles & certain desert
grasshoppers.
– Can also function in an anti-aggregation
mode when sufficient individuals are
present.
Herbivore induced plant volatile (HIPV’s)
• Produced by plants when herbivores feed on
them
• Pulls in natural enemies and increases
biocontrol
• i.e. winter green (methyl salicylate)
“Social Pheromones”
• Best known in the social Hymenoptera,
most especially the honey bee.
“Queen Substance”
• first elucidated in the 1950ties
• chemically complex (long chain fatty
acids)
• from the mandibular glands of a gyne
“Social Pheromones”
• Gynes have a dilemma
– Must maintain their reproductive status!!
– Do this in two ways:
• suppress ovarian development by daughters
• prevent daughters from replacing her.
– Solution
• chemo-sterilization
Key Points:
Chemical communication
• What is the difference between semiochemicals
and pheromones
• Describe two modes of action of pheromones
• How can sex pheromones improve our food
quality
• Name three pheromones and how they work
• Define Intra specific and Interspecific
• How does an HIPV work