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Insect Behavior

General Entomology

Fixed Action Patterns (FAP’s)

Genetically programmed behaviors

* elaborate courtship and mating rituals

* intricate nest building behaviors

* tool use (Ammophila, a sand wasp, tamps its nest entrances and weaver ants use their larvae

to sew together tree nests)

* migration routes of monarchs

Often condition dependent

Insects are great examples of engineered flexibility

* FAP's are condition dependent

* built-in flexibility

- Example: calling rate of field cricket as a f(x) temp:

T = 50 + (n-40/4)

* Example: ethogram or reaction chain for Physiphora demandata

- several paths and outcomes are possible given different stimuli, hormonal states, etc.

- reaction chains with pre-programmed behavioral flexibility

Endogenous Rhythms

* many insect behaviors occur on a 24-clocklike basis

* these are often referred to as Circadian rhythms, literally meaning "around one day"

* some insects only active for brief intervals each day

1. walking behavior in crickets (they get restless at night)

- hormonally induced Circadian rhythm (probably) the common control

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2. ghost moths fly only for 20 minutes at twilight

3. emergence of adults is often closely timed to some part of day: some morning, some

nocturnal, etc.

4. honey bee foraging activity

- bees showed up at Carl von Frisch’s tea at the same time every day at 10:00 AM

von Frisch discovered Circadian rhythms when bees arrived at 10:00 AM but tea and

sweets were late and had not yet been brought by the housekeeper.

* biological clocks entrained by

- protocerebrum and interneurons

- ocelli appear important in setting the internal clocks of insects

Orientation

* taxes: directed movements

* kineses: undirected movements, but where speed or freq. of turning is determined by

stimulus strength

* responses may be positive or negative

e.g.., negative phototaxis: insect turns a lot when there is much light;

positive phototaxis moves less with reduced light or flies towards light

Common taxes:

- photokinesis

- geotaxis

- directed movement with respect to gravity

- ants use this extensively; all ground dwellers

- anemotaxis

- movement with respect to air movement (wind direction)

- insects orienting to pheromones

- phototaxis

- many diurnal insects are positively phototacic

- astrotaxis

- orienting to sun or moon (includes polarized light)

- see Figure 7-7 from Evan’s Insect Biology

- chemotaxis

- orientation to taste or odor

- phonotaxis

- orientation with respect to sound

Klinotaxic behaviors: movements dependent on stimulus gradient:

e.g., light, chemical (pheromone), sound, etc.

FAP’s/behavioral actions are often condition-dependent

* hungry ant: positively phototactic, negatively geotactic

* well-fed ant: negatively phototactic, postitively geotactic

* any given behavioral actions will be dependent upon

- stimulus (e.g., bright or dark)

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- age, sex, etc.

- hormonal states

- physiological state (e.g., hungry or sated)

- previous experience (learned behavior)

Learning and Memory in Insects

* learning = changes in behavior as a result of previous experience

* most insects (cockroaches) begin forgetting soon after they learn something

* honeybees hold memories up to 14 days

* few insects selected to learn over long periods (life too short)

Location of Learning

* principally in the protocerebrum

* some learning in the mushroom bodies

* but some learning in thoracic ganglia in cockroach = ganglionic learning

What do insects learn?

* maze-learning: some can learn: ants and cockroaches

* some insects have remarkable abilities to learn some things more closely tied to their

survival:

1. Honeybees learn (four) colors and shapes reasonably well

2. Heliconiine butterflies (long wing butterflies)

- trapliners in tropics

3. Sand Wasps and ground-nesting bees

- orientation flights

- rapid capture of complicated surface details

- some easily fooled (Ammophila): move one or two key markers and all is lost

- others not easily fooled (Bembix) (digger wasp that nest on open sands)