Insect Biology: Adaptations, Behaviors, and Ecology

Insect Defenses Against Predators

Three Plant Mechanisms to Defend Against Insects

• Physical: Thick walls
• Chemical: Phytochemicals that kill insects
• Entrapment: Pitcher plants

How Insects Overcome Physical Defenses

• Specialized mandibles
• Evolution
• Immunity to phytochemicals
• Specialization to survive the digestive liquid of pitcher plants

Insect Parasitism

Endoparasites

Approximately 20% of insect orders include endoparasites. Some orders that include endoparasites are:

• Hymenoptera
• Diptera
• Strepsiptera

Ectoparasites

Some orders that include ectoparasites are:

• Anoplura
• Mallophaga
• Siphonaptera

Three Challenges Faced by Endoparasites

• Respiration
• Excretion/getting rid of toxic nitrogenous waste without killing the host
• Avoiding the host's endocrine system

Insect Social Behavior

Subsocial Behavior

Subsocial behavior includes egg guarding, building nests, provisioning of offspring with food, and overlap of generations.

Examples:

• Blattodea (cockroaches)
• Mantodea
• Embioptera (webspinners)
• Dermaptera (earwigs)
• Coleoptera
• Hemiptera

Eusocial Behavior

Eusocial behavior includes communication, reproductive division of labor (caste system), cooperative brood care, and overlap of generations.

Examples:

• Blattodea (termites)
• Bees (Halictidae/Apidae)
• Paper wasps (Vespidae)
• Ants (Formicidae)

Insect-Borne Diseases and Conservation

Malaria

Malaria is caused by the protozoan Plasmodium. Symptoms include fever, headache, chills, arthralgia, myalgia, and a rosy rash. Vector control methods, such as biocontrol, are preferred over insecticides. Globalization can lead to an increased spread of diseases.

American Burying Beetle (ABB) Decline

The decline of the American burying beetle is primarily due to a lack of suitable carrion. A suitability survey conducted over the last four years concluded that habitat restoration should precede the reintroduction of the ABB. Factors contributing to the decline include habitat loss, pesticide use, and climate change. Solutions include restoring habitat and the population of carrion animals and reducing the number of predators.

Niche Partitioning Among American Burying Beetles

Each species utilizes different types of carrion and becomes active during different times in the season. Phenotype refers to physical appearance/behavior, while genotype refers to genetic makeup (e.g., brown vs. green beetles).

Insect Symbiosis

• Stick bugs: Gongylidia/Mycangia (fungi garden/cavity)
• Mycetocyte: Microorganisms for digestion

Insect Decline and Pest Management

Insect Decline Measurement Methods

• Biomass
• Number of individuals
• Number of species

Three Modes of Transmission of Yersinia pestis to Humans

• Bite from an infected flea
• Inhalation of airborne bacteria
• Scratching of feces from an infected flea into a wound

Whirligig Beetle Locomotion

Whirligig beetles can reach speeds of 100 body lengths per second. The hind leg captures vortices generated by the mid leg, which adds additional forward thrust for swimming. This is a form of lift-based propulsion.

Integrated Pest Management (IPM)

IPM focuses on monitoring pest populations, reducing pesticide applications, and suppressing pest populations.

Insect Orders and Their Feeding Habits

• Odonata (dragonflies): All predatory
• Orthoptera (grasshoppers, katydids, crickets): Both predatory and herbivorous
• Grylloblattodea (ice crawlers): Scavengers
• Mantophasmatodea (rock crawlers): Predatory
• Phasmatodea (walking sticks): Herbivorous
• Mantodea (praying mantises): Predatory
• Blattodea (cockroaches and termites): Diverse feeding habits
• Thysanoptera (thrips): Fungi, some herbivorous
• Psocodea (parasitic lice): Chewing and sucking
• Hemiptera (plant hoppers, tree bugs, aphids): Plant fluid feeders and predatory
• Hymenoptera (bees, wasps, and ants): Parasites and predatory
• Strepsiptera (twisted-winged parasites): Endoparasitic
• Siphonaptera (fleas): Blood-sucking ectoparasites
• Diptera (flies): Very diverse; species can be ectoparasites, endoparasitoids, herbivores, detritivores, predators, and pollinators
• Lepidoptera (butterflies and moths): Liquid feeders using a proboscis

Insect Adaptations

• Polyethism: Functional specialization
• Hyperparasitism: One parasite attacking another parasite
• Autotomy: Ability to lose limbs
• Aposematism: Bright colors to deter predators