I. Ethology of Insects II. Patterns of Behavior III. Modifications IV. Operation V. Genetic Basis VI. Life History

Transcription

1 Insect Behavior

2 I. Ethology of Insects II. Patterns of Behavior III. Modifications IV. Operation V. Genetic Basis VI. Life History

3 I. Ethology of Insects Ethology is the comparative study of behavior We assume that behaviors will maximize an individual s fitness How much is innate vs. learned? Niko Tenbergen

4 Questions Proximate Causation: What are the stimuli that elicit the response, and how has it been modified by recent learning? Development: How does behavior change with age? Ultimate Evolution: How might have behaviors arisen through the process of phylogeny? Function: How does the behavior impact an animal's chances of survival and reproduction?

5 II. Patterns of Behavior A. Reflex B. Fixed-Action Patterns C. Modal-Action Patterns D. Orientation M. Olson

6 A. Reflex Basic unit of insect behavior One kind of receptor, when stimulated, causes a specific group of muscles to contract stimulus-response rule Combinations result in coordinated movements Releaser - the stimulus that triggers a particular set of movements Threshold the minimum level of stimulus required to initiate (release) a response

7 B. Fixed-Action Patterns Stereotyped; exactly the same each time it is performed M. Olson

8 C. Modal-Action Patterns Less stereotyped; varying, adjustable (i.e. walking, flying) M. Olson

9 D. Orientation - modification of body position/movement with respect to some variation in the distribution of environmental stimuli Kinesis unoriented action that varies according to stimulus intensity Ex. Making more turns to remain in favorable temperature zone Taxis positions and movements with respect to the source, direction, or gradient of a stimulus Ex. Lunar navigation (menotaxis); sex pheromones

10 Chemotaxis

11 III. Behavioral Modifications Internal control: Circadian rhythms, feedback loops, hormonal/life stage changes A. Habituation B. Associative Learning C. Latent Learning D. Insight Learning M. Olson

12 A. Habituation A diminished response to a stimulus after repeated exposures w/ no relevant consequences M. Olson

13 B. Associative Learning Classical conditioning new stimulus (neutral) becomes associated with old stimulus

14 B. Associative Learning Operant conditioning associate action with a positive or negative consequence ex. Trial-and-error learning

15 C. Latent Learning Ex. Digger wasp Familiarity with relationships among neutral stimuli no immediate consequences Role of memory

16 D. Insight Learning Information is combined from several learning experiences and applied to a situation never before encountered. Are insects capable of cognition? Ex. Honey bee mental maps M. Olson

17 IV. Operation and Structure Dominant/subordinate status Depends on internal causal state (reproduction, feeding, or migration) and external stimuli A. Thresholds and releasers B. Chaining C. Behavioral Models

18 A. Thresholds and Releasers A stimulus elicits a behavioral response Releaser a stimulus that triggers a specific behavior Threshold the minimum level of stimulus required to initiate (release) a response Appetitive behavior sequential releaser; oriented movements bring the insect to the next releaser

19 B. Chaining Each successive behavioral stage depends on the occurrence of an appropriate new stimulus Performing dominant behavior induces feedback which then reduces its status, allowing performance of previously inhibited behaviors Appetitive sequences are a type of chaining involving sequential releasers Ex. Sphex digger wasp

20 B. Chaining What happens when an inappropriate stimulus is introduced during a chain sequence? Sphex digger wasp

21 C. Behavioral Models Hierarchical Control system models

22 Gene control V. Genetic Basis Behavioral traits usually polygenic Genes have pleiotropic effects However, some behaviors can be broken down into actions controlled by specific genes

23 V. Genetic Basis Phylogenetic applications Can be used in evolutionary reconstructions to determine relatedness Just like a morphological or molecular trait, behavioral traits are heritable and shared among related taxa

24 VI. Life History A. Fitness B. Reproductive Behavior C. Exploiting Resources D. Migration

25 entomologist behavior Thanks to Michael Olson for photos!

26 Reproductive Behavior & Communication

27 Steps in Reproductive Behavior 1. Mate location 2. Species recognition 3. Mate acceptance 4. Copulation/Transfer of sperm 5. Post-copulatory behaviors 6. Parental care

28 Aggregation behavior Advantages Increased mate choice Outbreeding 1. Mate Recognition Swarming aerial stations Lekking substrate defense without resources Usually males, but exceptions Protection from predators

29 Ramphomyia longicauda long-tailed dance fly Females expand in swarm to attract males Sex role reversal male investment Funk and Tallamy 2000, Animal Behavior

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35 Species Recognition PHEROMONES Play large role in bringing sexes together Sex attraction pheromones Acts at a distance Courtship pheromones Close up action Pheromones mostly females that produce but exceptions Species Specific cocktails w/ varying concentrations in different closley related sp COURTSHIP DISPLAYS Also involved w/ mate acceptance

36 Bombyx mori (silkworm moth) Females produce pheromone called bombykol Males have long pectinate antennae to sense Females cease bombykol production after mating Females mated with penis-removed males, only a penis, or had inflated bursa copulatrix produced little bombykol Artificial insemination does not greatly affect bombykol production

37 Territoriality Substrate defense with resources Can be within an aggregation, but not needed Males defend: Food resources Oviposition sites Reduce conflict between males

38 Leistotrophus versicolor rove beetle Two male mating strategies dominant, female mimic Dominant male will switch to mimic if encounters larger male Forsyth and Alcock 1990, Behavioral Ecology and Sociobiology

39 Panorpa scorpionflies Three male mating strategies: 1. Dominant males defend dead insect prey item 2. Intermediate-sized males produce & defend saliva mound 3. Sneakers wait and steal matings If remove dominant males, saliva-guarding males claim insect gifts Sneaker males usurp abandoned saliva mounds Thornhill 1981, Annual Review of Ecology and Systematics

40 3. Mate Acceptance Nuptial feeding food resource offered to female Male regurgitation Glandular product (spermatophore) Cannibalization Nuptial gift prey item All provide nourishment Directly for female paternal investment Prevent female interference buying time

41 Kawanaphila katydids spermatophore + changing sex roles When food sources scarce, spermatophores costly to produce females compete for male mates When food sources abundant, males can easily produce spermatophores,, and compete for female mates Gwynne & Simmons 1990, Nature

42 Sexual Selection Natural selection trait associated with survival Sexual selection trait associated with reproductive competition, not survival Body size Color Combat characters Call/song Larger males often monopolize females Female choice drives differential success

43 Arctiid Moths Courtship display - Males inflate apparatus at tip of abdomen Release sex pheromone

44 Curculionidae Horns & snouts used in male-male combat for mates

45 4. Copulation Sperm transfer Internal/external fertilization Traumatic insemination Sperm competition Sperm precedence Battle of sexes intersexual conflict Sperm storage - spermatatheca

46 Calopteryx maculata black-winged damselflies

47 5. Post-Copulatory Behaviors Copulatory plugs Male may release coagulant into female to prevent future matings stink plugs Mate Guarding Physical prevention of subsequent matings Chemical inhibition - e.g. bowflies Oviposition Bare eggs Ootheca Egg burying Nest construction Parasitoids

48 Copulation Sperm transfer Internal/external fertilization Traumatic insemination Sperm competition Sperm precedence Battle of sexes intersexual conflict Sperm storage - spermatatheca

49 Post-Copulatory Behaviors Copulatory plugs Male may release coagulant into female to prevent future matings stink plugs Mate Guarding Physical prevention of subsequent matings Chemical inhibition - e.g. bowflies Oviposition Bare eggs Ootheca Egg burying Nest construction Parasitoids

50 Parental Care Egg/early instar attendance Primarily female role, but exceptions (eg. Belostomatids) Orthopteroid orders, Embiidina, Psocoptera, Thysanoptera, Hemiptera, Coleoptera & Hymenoptera Functions Aerate Fend off predators Prevent parasites Maintain water levels Herd young Feed young

51 Cicada killer wasps Dig burrow in which to bury eggs Kill cicada and leave for young to feed on upon hatching

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