Spiders are one of the most ubiquitous creatures on Earth, yet something as commonplace as squishing a spider leaves many wondering—do spiders feel pain? If you’re rushed for time, the short answer is: researchers believe spiders likely sense and react to damaging stimuli, but the debate continues over whether they feel “pain” as humans understand it.
This article will examine the latest scientific research into spider neurobiology to unravel what happens when spiders get squished. We’ll cover arguments from experts on both sides of this debate over arachnid sentience and pain sensation. Key topics include:
• Spider brain structure and nervous systems
• Responses to negative stimuli and nociception
• Pain definitions and concepts in invertebrate biology
• Welfare considerations for spiders and other invertebrates
Spider Neurobiology and Behavior
Basic Spider Physiology
Spiders are invertebrates that belong to the arachnid family. They have a centralized nervous system, consisting of a brain that processes sensory information and controls behaviors. The spider brain is relatively simple compared to vertebrate brains, but still capable of basic learning, memory formation, and complex behaviors.
In addition to the brain, spiders have nerve cords and nerve ganglia that innervate their limbs and body segments. Sensory organs on the legs called slit sensillae detect chemical, mechanical, and vibration stimuli. Spiders also have simple eyes for detecting light and movement.
Nervous System and Sensory Reception
A spider’s nervous system controls behaviors like web building, hunting, courtship, and reactions to threats. Sensory organs on the legs and body surface called slit sensillae detect chemical, vibration, humidity, and mechanical stimuli.
These sensory inputs are processed by the central nervous system to initiate and coordinate the spider’s behavioral responses.
In addition to slit sensillae, most spiders have 6-8 simple eyes that detect light, movement, and form basic images. The jumping spider family has very acute vision from their large front eyes with movable retinas.
Overall, spiders rely heavily on vibratory, chemical, and tactile signals to sense their environment and prey.
Reactions to External Stimuli
Spiders exhibit a range of behaviors in response to external stimuli detected by their sensory systems. These include:
- Quick withdrawal from contact with predators or threats
- Attacking and biting prey or threats
- Vibration of web to confuse prey
- Death feigning or catatonia when handling threats
- Construction and repair of webs in response to damage
- Courtship rituals like web plucking, tapping, and dancing
The external stimulus provoking the greatest reaction is bodily injury like being squished. Spiders will vigorously pull away, bite, release venom, play dead, or get highly aggressive when physically harmed. Their brains are wired to interpret crushing pressure as a severe threat.
Do Spiders Feel Nociception and Pain?
The question of whether spiders and other invertebrates feel pain and suffer has long been debated in the scientific community. Here is an overview of the evidence surrounding nociception and pain in these creatures.
Nociception vs. Pain in Invertebrates
Nociception refers to the detection of potentially harmful stimuli by sensory neurons called nociceptors. Even simple organisms like bacteria have nociceptive abilities. However, the experience of pain involves complex neural processing and emotional responses, which require more sophisticated cognitive abilities.
While insects and spiders do exhibit nociceptive reflexes, many argue they lack the neural complexity for conscious pain perception. Their small brain size and simple neural organization is believed to limit their capacity for suffering.
Debates on Spider Sentience
Some scientists acknowledge spiders may have a basic capacity for suffering. Studies show nociceptor activity in spiders triggers endogenous opioids and benzodiazepines, suggesting an evolved response to nociceptive pain.
Jumping spiders also exhibit complex cognitive behaviors like curiosity, deception, and attention that could indicate sentience.
However, most entomologists maintain insects and arachnids operate primarily on pre-programmed instinct rather than conscious awareness due to their rudimentary brains. Some hold that anthropomorphic projections of pain and suffering onto invertebrates are unscientific.
Stress Responses to Injury
Injured spiders do exhibit stress responses consistent with nociception, if not pain. When researchers severed the legs of orb-web spiders, the spiders showed limping, slowed movement, decreased web-spinning, and reduced prey capture.
Curling up of the body and limping are common stress behaviors in injured spiders.
While these stress responses indicate nociceptor activation, they do not confirm conscious pain experience. However, appropriately anaesthetizing spiders before injury prevents these stress reactions, suggesting anesthetics may still relieve suffering even if spiders lack the cognition for true pain.
Considerations for Spider Welfare
Pest Control and Humane Treatment
While spiders can be seen as pests in homes, more humane approaches should be taken when removing them rather than immediately squishing them. Catching spiders in a cup and releasing them outside prevents needless suffering.
Many extermination companies now offer humane spider removal services that avoid pesticides and vacuum spiders up for outdoor relocation.
New research also shows that spiders may feel pain and distress when squished. One 2021 study found that jumping spiders had avoidance behaviors when exposed to potentially painful stimuli, suggesting an ability to experience negative sensations.
One of the study’s authors argued, “the most ethical choice is to avoid killing spiders unnecessarily.”
Teaching Children Compassionate Behaviors
Parents and teachers should guide children to appreciate spiders and treat them with care rather than immediately squishing them out of fear or disgust. Educational resources like illustrated spider field guides can teach kids about different spider species and their behaviors.
Getting children interested in spiders as fascinating creatures rather than “creepy crawlies” promotes more empathy and compassion.
Simple hands-on activities can also teach gentle handling of spiders. For example, letting children hold a harmless pet tarantula, under supervision, helps overcome phobias. Such direct contact allows kids to see that spiders are living beings that deserve ethical treatment even if they look different from us.
Minimizing Suffering in Laboratory Research
Spiders and other invertebrates are frequently used as research subjects in laboratories. While this research provides benefits for science and medicine, scientists have an ethical responsibility to minimize suffering. Guidelines include:
Several organizations offer certification programs for more humane laboratory animal practices involving spiders and other invertebrates. For example, the Association for Assessment and Accreditation of Laboratory Animal Care International has a pilot program for assessing invertebrate welfare in research settings.
Conclusion
While many compelling pieces of evidence suggest spiders have adverse reactions to injury, the debate continues whether these stimuli constitute “feeling pain” in the way humans experience it. Ultimately, understanding where to draw the line on invertebrate sentience has ethical implications in how we treat spiders and other creatures who share our world.
