The Wonders of Instinct: Chapters in the Psychology of Insects Informative Summary


“The Wonders of Instinct: Chapters in the Psychology of Insects” by J.H. Fabre, a renowned entomologist, offers a captivating exploration of the intricate world of insect behavior. Through detailed observations and ingenious experiments, Fabre challenges prevailing notions about insect intelligence, demonstrating the remarkable complexity and sophistication of their instincts. He meticulously documents the lives of various species, including the Green Grasshopper, the Empusa, the Capricorn Beetle, and the Burying-beetle, highlighting their unique hunting strategies, building techniques, and surprising levels of “reasoning” abilities.

Fabre also examines the social structures of insects, specifically focusing on the collaborative efforts of the Pine Processionary caterpillar and the unique parenting strategies of the Lycosa spider. He delves into the delicate balance of nature, highlighting the role of insects as both destructive pests and crucial elements in the ecosystem.

Key findings:

  • Insects exhibit remarkable complexity in their instincts, demonstrating a level of “reasoning” and foresight that challenges traditional notions of animal intelligence.
  • Insect behavior is highly adaptable, with individuals adjusting their strategies based on environmental factors and challenges.
  • The relationship between insect and environment is crucial, with species demonstrating remarkable adaptations to their specific habitats.


  • Instinct vs. Intelligence: The text explores the blurred line between instinct and intelligence in insects, demonstrating that their behaviors often go beyond simple, innate responses.
    • Details: Fabre uses numerous examples to show how insects seem to make deliberate decisions and anticipate future events, even when lacking complex senses or cognitive capabilities.
  • The Power of Observation: Fabre emphasizes the importance of meticulous observation and experimentation in understanding the intricacies of insect behavior.
    • Details: Fabre’s detailed descriptions and insightful analysis of insect behaviors, combined with his clever experiments, offer a new perspective on the world of insects.
  • The Importance of the Environment: Fabre demonstrates how the environment significantly influences insect behavior and development.
    • Details: The text showcases how insects adapt their strategies, food choices, and even physical characteristics based on the specific conditions of their habitats.
  • Nature’s Interconnectedness: Fabre highlights the intricate interconnectedness of nature, showing how insects play crucial roles in the ecosystem, even as they can cause significant damage to crops.
    • Details: The text provides various examples, including the relationship between the Burying-beetle and the soil’s health, and the complex interactions between the Cabbage Caterpillar and its predators.

Historical Context: The text was written during a time when the prevailing scientific view considered insects to be simple creatures with limited intelligence. Fabre’s work challenged this view, presenting evidence for a more complex and nuanced understanding of insect behavior.


  • The Green Grasshopper primarily feeds on Cicadas, preferring their sugar-rich abdomen.
  • The Empusa larva, known as the “Devilkin” for its strange appearance, is a fierce predator despite its small size.
  • The Capricorn Beetle larva spends three years in its oak-trunk home, eating its way through the wood.
  • The Burying-beetle is not a scavenger, but a gravedigger, burying its prey whole to provide food for its larvae.
  • The Pine Processionary caterpillar leaves a trail of silk as it moves, using it as a guide to navigate its environment.
  • The Narbonne Lycosa spider builds a burrow with a distinctive curb made of grass, twigs, or even stones.
  • The Eumenes wasp constructs a dome-shaped nest made of mud and small stones, often adding decorative elements like quartz pebbles.
  • The Osmia bee uses either mud or a paste made from chewed leaves to build partitions in its nest.
  • The Glow-worm uses a specialized set of mandibles to administer an anesthetic to snails, making them immobile before feeding.
  • The Glow-worm’s light is produced through a chemical reaction involving oxidation of a special substance.
  • The Cabbage Caterpillar is a voracious eater, consuming large quantities of cabbage leaves until it reaches maturity.
  • The Microgaster glomeratus, a tiny wasp, parasitizes the Cabbage Caterpillar by injecting its eggs into the caterpillar’s eggs.
  • The Microgaster larva feeds on the caterpillar’s blood, eventually killing it.


  • The Green Grasshopper consumes nearly the entire abdomen of its Cicada prey.
  • The Pine Processionary caterpillar can form processions up to 12 yards in length, with hundreds of individuals.
  • The Lycosa spider’s egg-sac is the size of a cherry.
  • The Eumenes Amedei wasp can lay 5-10 caterpillars in a single nest.
  • The Microgaster glomeratus can lay up to 65 eggs in a single Cabbage Caterpillar egg.
  • The Glow-worm larva spends the winter months underground, returning to the surface in April.


  • Instinct: An innate behavior that is not learned, often complex and adaptive.
  • Prolegs: The fleshy, non-jointed appendages found on some caterpillars.
  • Spinnerets: The organs on a spider’s abdomen that produce silk.
  • Chrysalis: The immobile stage of a butterfly’s life cycle, enclosed in a hard case.
  • Ovipositor: The organ on a female insect used to lay eggs.
  • Larva: The young, immature stage of an insect.
  • Nuptial: Relating to marriage or mating.
  • Anaesthesia: The state of being insensible to pain.
  • Ovary: The female reproductive organ, where eggs are produced.
  • Pupa: The immobile stage of an insect’s life cycle, typically after the larval stage.


  • The Green Grasshopper: This insect demonstrates its predatory instincts by catching and consuming Cicadas, primarily targeting their sugar-rich abdomen.
  • The Empusa: This peculiar insect uses its distinctive head-dress as a defensive weapon, butting its prey to deter attacks.
  • The Capricorn Beetle: The larva of this beetle exhibits impressive foresight by constructing a special chamber for its transformation and preparing an exit hole for the adult beetle.
  • The Burying-beetle: This insect demonstrates remarkable cooperation, working together to bury large prey, even if it requires displacing or breaking obstacles.
  • The Pine Processionary Caterpillar: This caterpillar exemplifies the power of social behavior, using a trail of silk to guide its movement and maintain unity within the group.
  • The Narbonne Lycosa Spider: This spider demonstrates a surprising level of architecture, building intricate burrows and elaborating its entrance with various materials, including wool.
  • The Eumenes Wasp: This wasp demonstrates its artistry through the construction of its dome-shaped nest, often incorporating decorative elements like quartz pebbles.
  • The Osmia Bee: This bee exhibits flexibility in its nest building, adapting to various housing options and demonstrating an ability to control the sex of its offspring.
  • The Glow-worm: This insect uses a specialized set of mandibles to anesthetize snails, making them immobile before feeding, showcasing a remarkable skill in incapacitating its prey.
  • The Cabbage Caterpillar: This caterpillar exhibits insatiable gluttony, consuming large quantities of cabbage leaves, showcasing its remarkable capacity for growth.

Conclusion: “The Wonders of Instinct” offers a fascinating glimpse into the complex and often surprising world of insects. Fabre’s meticulous observations and experiments overturn traditional assumptions about insect intelligence, demonstrating their remarkable abilities for problem-solving, planning, and adapting to their environment. The text reveals a rich tapestry of insect behavior, showcasing their intricate relationships with the natural world and their vital role in the ecosystem. Through Fabre’s lens, we gain a deeper appreciation for the diversity, complexity, and hidden marvels of the insect world.

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