University of Michigan Biological Station

Biology 442 - Biology of Insects

Lecture Notes - Ecological Interactions of Insects

1. Interactions on same trophic level.
   1. Competition - for many years thought to be the major structuring force in all communities.
      1. Definitely occurs in insects - most common among insects using discreet resources.
      2. Examples - Tribolium confusum and T. castaneum, Megarhyssa and other parasitoids, scale insects
      3. Does not seem to be common in most herbivores or predators - evidence from life tables indicates that competition does not cause most mortality.
2. Interactions with lower trophic levels.
   1. Herbivory
      1. Structured by plant secondary chemicals - based on herbivores escaping competition.
      2. Possibility of being driven from above - based on herbivores escaping parasitoidism and predation
      3. Major groups
         1. Lepidoptera
         2. Chrysomelidae, Cerambycidae, Curculionidae and other Coleoptera
         3. Orthoptera
         4. Chloropidae, Anthomyiidae and other Diptera
         5. sawflies, Cynipidae and a few other Hymenoptera
   2. Predation
      1. Insects that kill and eat others - usually smaller than they are
      2. Important things - searching ability, hiding ability, aposematism, mimicry
      3. Predator styles - searchers (Carabidae), stalkers (Mantodea), trappers (Myrmeleontidae)
      4. Major groups
         1. Mantodea
         2. Carabidae, Cicindelidae, Coccinellidae and other Coleoptera
         3. Asilidae
         4. Neuroptera
         5. Odonata
         6. Misc. other groups
   3. Parasitoidism
      1. Insects that feed on insects of similar or bigger size, but do not kill until they have completed development
      2. Similar considerations as before - also see competition with other parasitoids
      3. Hyperparasitism - see handout
      4. Major groups
         1. Braconidae, Ichneumonidae, Chalcidoidea
         2. Tachinidae
         3. Meloidae
   4. Parasitism
      1. Insects that are smaller than host - do not kill host - may be on other groups
      2. See extreme specializations and adaptations - winglessness, paedogenesis, blood feeding
      3. Major groups
         1. Blood sucking flies (not true parasites) - Culicidae, Ceratopogonidae, Tabanidae, Muscidae - see handout of diseases transmitted
         2. Fleas - only parasites as adults - bridge gap to true parasites
         3. Lice - true parasites
         4. Strepsiptera - only real one on other insects
         5. Flies living inside tissues - Calliphoridae as would cleaners, screwworm, bots, warbles, myiasis
3. Interactions with higher trophic levels.
   1. Prey for other species (see example of food chain)
   2. Who eats insects?
      1. Bats, shrews and moles
      2. Trout, Gambusia
      3. Birds - specialized niches, e.g. swallows and flycatchers, woodpeckers, thrushes - nestlings eat 2x their weight in insects each day.
      4. Other insects
   3. Defenses of insects
      1. Primary defenses (passive defenses) - act before attack
         1. Crypsis - generalized and special - salt and pepper moth in England, by 1895 had shifted to melanics and now almost back.
         2. Aposematism - warning coloration - warns of bad taste or potential for harm such as sting
         3. Mimicry - Batesian and Mullerian
      2. Secondary defenses
         1. Flight patterns - escape, sudden landing
         2. Death feigning - beetles
         3. Poisons - delivered by hairs, spines, stings - may just irritate or poke
         4. Detaching body parts - e.g. scales on butterflies and moths (escape from spider webs)
         5. Deflection of attack - hairstreaks
         6. Startles - sight and sound
         7. Chemicals - bombardier beetles
4. Scavengers
   1. Saprophages - Collembola, many flies and beetles, even some Lepidoptera
   2. Necrophages - carrion eaters, beetles and flies
   3. Coprophages - dung, beetles and flies

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