Insect Behavior Final

foraging

food-obtaining behavior, recognizing, searching for, capturing, eating food items

all animals

carbohydrates, fats, amino acids, minerals, and vitamins are essential for

cholesterol (cannot synthesize), sodium (particularly important to herbivores)

essential nutrients that are specific to insects

sweat bees feeding on human sweat for sodium and other minerals

an example of an insect feeding for sodium

puddling: insects gather at the edge of a puddle for salt and amino acids

an example of insects gathering nutrients

surface texture, visual cues, chemical cues

how do insects recognize and accept their food?

some wasps (Trichogramma evanescens) will only parasitize objects that are firm enough for it to walk on

example of surface texture recognition

proper positioning for egg laying, physical contact assists with host suitability, relying on walking to explore a host is very efficient for small insects

why use surface texture in foraging?

tsetse flies are drawn to their host using a combination of visual and chemical cues: movement, dark color, shape of large mammals, CO2, sweat, body odors, heat

example of visual cues in foraging

potato beetle lives on plant that contains toxic alkaloids, larvae have not adapted to the alkaloids yet, rely on olfactory receptors to detect harmful alkaloids, if receptors (palps and antennae) are removed, they will eat the harmful alkaloids

example of chemical cues in foraging

insects make “perfect” foraging decisions

to test if insects balance their diet, you must assume that

age, previous experience, nutritional needs, development stage, etc

what are some factors to consider when testing insect foraging?

choice experiment of different types of pollen (yes they can)

how to test if insects can balance their diet?

reduced competition, efficient, may provide protection from predators through plant toxins, plant-insect coevolution, the plant serves as mating site (drawbacks: what if host goes extinct? environmental changes?)

most insects are herbivores and specialists, why?

favored

specialization is _____ by natural selection

specialists

(foraging) most insects are

single host (parasitic wasps, leaf mining larvae)

extreme specialists are limited to a

mosquito larvae feed on plankton, adult female = blood, adult male = nectar

example of different feeding behavior throughout life stages

leaves in sugar are tied up in cellulose (strong connections btwn cellulose and glucoses), pollen and nectar limited to certain flowers/hours/seasons, plants may have defense mechanisms

challenges of herbivorous insects

gut microbes

digestion of cellulose requires specific enzymes that are acquired by having

by licking the anus of the adults

how do young termites acquire symbiotic microbes?

must find a way to capture prey, such as actively hunting in dragonfly larvae or ambushing

challenges in carnivores

relatively rare in insects, difficult lifestyle, example = ants, use cooperative hunting

challenges in omnivores

saprophagous

feed on carrion, decayed plant, and animal material, biggest challenge is to find resources (“first come first serve”)

blood feeders

need to find the host, digest large amount of food at once, and resist potential pathogens

mouthparts (butterflies, bees)

adaptation of _____ helps in foraging

optimal foraging theory (OFT)

views foraging behavior as a compromise between benefits of nutrition and costs of obtaining food to maximize fitness (natural selection should favor foraging behavior that minimizes costs and maximizes benefits) (behavior may not always be optimal)

currency

(foraging) the “goal,” more food per unit time, must correlate with fitness, often maximize rate of net energy intake

contraints

factors that limit the forager’s ability to maximize the currency, intrinsic (limitations in ability, such as running speed, tolerances), extrinsic (imposed by environment, such as prey density)

decision

(foraging) maximizes the currency under the constraints of the environment, behavioral options such as pursuing prey or not

outputs of OFT

identifies currency and constrains (ex: number of food items, energy spent), makes assumptions explicit (ex: the more food items the better), generates quantitative and testable predictions (ex: count items, count fitness), suggests new hypotheses if model doesn’t fit, becomes more complicated as function of the number of constraints/currency

prey types (predators encounter various species, diff sizes etc), search times (time spent searching for prey), handling time (time spent subduing prey and consuming it), energy return (energy gained from consumption), optimal prey choice (model assumes predator will choose prey that maximizes gain and minimizes time/risk)

prey choice model basic principles (which prey to capture?)

patch choice model

when is the optimal time to leave a patch? decision = stay or leave a patch, currency = maximizing profitability, constraints = time spent searching patches or traveling between patches, we assume perfect knowledge (energy gain in a patch and patch locations are known)

diminishing return

energy gain in patches shows ______ ______ but the optimal time in the patch also depends on the traveling time between patches

marginal value theorem (MVT)

stay in a patch until the benefit of staying is equal to the benefit of moving (if transit time is longer, stay in patch longer, if transit time is shorter, stay in patch less)

central place foraging

an extension of the marginal value theorem: insects typically leave a central place to forage and return to that place with food, insects needs to know when to leave patch and how much to carry back, the further the insect has to carry food, the longer it will remain in the patch and the more it will carry

larger loads require more energy (used weights and found that bees were in fact maximizing profitability)

larger load in nectar that bees carry shows diminishing returns because

termites, leaf cutter ants with fungus to digest cellulose, cockroaches with symbionts that are transferred across generations in eggs

examples of digestion using symbionts

red queen hypothesis

organisms must constantly increase their fitness to compete with other evolving organisms in a changing environment

insectivores, parasites, microscopic predators (and humans sometimes)

who eats insects?

no

is the exoskeleton of the Hercules beetle a behavioral defense?

passive messages (camouflage, mimesis, aposematism, mimicry, morphology couple with behavior is usually low energy cost, active messages (startling, jamming, behavioral defense, social defense)

defense strategies

seek the appropriate background or include motion shifting

static coloration is a behavioral anti-predator defense only if the insects

by dorso-ventral flattening

how is reducing shadows achieved?

countershading

light source makes the upper side look lighter, ability to hide/be seen in different angles

mimesis (orchid mantis disguised as orchid)

resembling an object in the environment that is uninteresting to the predator

skipper butterfly caterpillars eject feces from their hiding spots to make it harder for parasitic wasps to find them, beetle larvae shielding itself with feces

example of crypsis by sanitation

Batesian mimicry

aposematic inedible model has an edible mimic, only works if false mimic is rare (predators will eat safe one and begin to think all are safe)

Mullerian mimicry

a group of species benefit from each other’s existence because they are all warningly colored in the same manner and distasteful, like in Batesian mimicry, the mimics are not necessarily related

UV-reflecting scales on dorsal wing surface, brief flash of UV with each downstroke of the wing, different signals by different species, serves as mating signals for males

behavioral aspects in mimicry

behavioral mimicry

fly mimics vespid by smelling with front legs to mimic antennae

startle display

a display made by a cryptic insect upon discovery, involving exposure of a startling color pattern or display, such as eyespots

snake mimicry in caterpillar, snowberry flies resemble jumping spider

startle display/intimidation examples

jamming

disrupting the echolocation of bats by clicking

feigning death

beetles, particularly weevils, are especially fond of this sort of acting (defense)

delayed chemical defense (class 1 compounds, ex: monarch butterfly)

chemicals with delayed reactions, occur after the prey item has been consumed, found in the hemolymph or other internal tissue of the insect, are often accompanied by an immediate-acting chemical or aposematic coloring

class 2 compounds (formic acid in ants, spines on caterpillar)

immediate acting chemicals affect the predator as it is handling the potential prey item, chemicals are secreted externally, tend to be volatile

bombardier beetle mixes different chemicals from different glands then injects them into an explosion chamber containing mostly water, within chamber is catalase, causes explosive reaction, 100C water

example of chemical defense

lipids

aphids secrete ____ to gum up mouthparts of arthropod predators

chemical defense in termites

many termites secret chemicals that harden when in contact with air, impairs movement of predators, termites preyed upon by ants emit a class II mimic of ant alarm pheromone

gregarious insects

chemically defended, aposematic insects tend to cluster rather than spread out in environment, will orient themselves in the best manner for optimally disseminating chemicals, sometimes form aggregations in defensive circles

herd allows individuals to hide, downside: many individuals are easy to spot, most aggressive individuals get safest spot in center

sociality as an anti-defense mechanism

social defense in mayflies

dilution effect, predators saturation, the more females emerging per day, the less likely any individual mayfly was to be eaten by a predator

successful reproduction, appropriate microclimate for growth of juveniles, minimum inter and intra species competition, maximal food availability, maximal survival

the right habitat allows for

habitat destruction, climate change and humans are largely responsible for this

what is the main cause for species decline?

both landscape and species affects preference, results can be used to improve conservation

habitat preference in bumblebees

paper wasps, chew and glue plant material together to form cells, small variation in building pattern can result in large differences in nest shape: flat comb vs. string like nest

example of next construction and architecture

string-like nests

cells are started near the top of the previous cell, long string-like structures that look like dead sticks, often found on garden shrubs or fences

flat comb nests

cells are started near the base of the previous cell, open combs appearance, underside of leaves or overhangs

build, take it with them

some insects ____ their home and ____

territorial space

crickets have a _____ for the purpose of mating

stability, choice of materials (feces, saliva, mud, chewed-up plant), internal design (tunnels and chambers strategically placed to distribute weight evenly), moisture is regulated to prevent structure from becoming too brittle/soft, maintenance, chimney effect for passive airflow

functional architecture in termite nests

parasitic wasp find its host using innate (response to frass) and learned (response to fruit cue) responses, bumblebee choice of cavity is innate, cockroach preference for darkness is genetic

habitat selection: nature vs. nurture

aggressive competition with other individuals over nesting

if appropriate nesting sites are scarce, this leads to

ideal free distribution theory

the number of individual animals that will aggregate in various habitats is proportional to the resources available in each

habitats differ in the resource they contain, individuals are aware of this and try to maximize fitness, individuals are free to move to

ideal free distribution assumptions