Overview of This common garden plant summons wasps as bodyguards
This NPR Shortwave science roundup focuses on adaptation in nature—both as defense and as a vulnerability. The episode covers three studies: how bean plants recruit parasitic wasps to attack caterpillars, how larger but less frequent rewards can speed up learning in mice, and how mosquitoes can be trained to associate DEET with food, revealing a potential weakness in a major repellent.
Bean Plants’ Chemical Defense: Calling in Wasp “Bodyguards”
Researchers found that common bean plants can detect caterpillar saliva and respond by releasing airborne chemicals that attract predatory and parasitoid wasps.
What happens
- When caterpillars chew on bean plants, a compound in their spit triggers the plant’s defense response.
- The plant releases a chemical signal into the air.
- That signal summons wasps, which either:
- eat the caterpillars, or
- lay eggs inside them, causing the larvae to be consumed from within.
Why it matters
- It’s a vivid example of plant-versus-animal warfare.
- The defense is highly specific: the plant responds to caterpillar saliva, not just any kind of damage.
- It adds to the broader understanding that plants have evolved sophisticated ways to defend themselves, from thorns and toxins to chemical signaling.
Faster Learning in Mice Through Bigger Rewards
A separate study in Science found that mice learned tasks faster when rewards were larger but less frequent.
What the researchers tested
- Mice were trained on tasks such as:
- associating sounds with rewards,
- pulling a joystick,
- turning a tiny steering wheel.
- Instead of giving small rewards often, researchers sometimes gave bigger rewards less often.
Main finding
- The bigger rewards produced a stronger and longer-lasting dopamine response.
- That seemed to keep the mice more engaged, improving learning speed.
- Researchers said they had been underestimating how efficiently animals can learn.
Why it matters
- The work may help improve future animal learning studies.
- It offers clues about how reward size and motivation affect learning, though it is not yet directly comparable to human learning.
Mosquitoes Can Learn to Associate DEET With Food
The final study explored a surprising vulnerability in DEET, the most widely used mosquito repellent.
Key finding
- Mosquitoes can be trained to associate the smell of DEET with a food reward.
- In experiments, mosquitoes learned to approach DEET after repeated pairing with sugar or blood.
How the study worked
- Researchers used a Pavlov-style conditioning setup:
- DEET smell = signal
- blood or sugar = reward
- After training, mosquitoes were drawn to DEET more often than expected, even approaching a human hand sprayed with it.
Important caveat
- This does not mean DEET has stopped working in real life.
- The researchers and outside experts stressed that:
- the mosquitoes had to be heavily trained,
- wild mosquitoes usually still avoid DEET,
- people should continue using DEET as directed.
Why it matters
- The study shows that mosquitoes have more flexible learning abilities than scientists expected.
- It also underscores how important mosquito repellents are for public health, since mosquitoes spread diseases such as malaria.
Big Takeaways
- Plants can actively recruit “bodyguards” by detecting specific insect saliva and releasing airborne signals.
- Reward structure affects learning: bigger, less frequent rewards may drive faster learning in mice.
- Mosquito behavior is adaptable, and even DEET can become part of a learned association under artificial conditions.
- The episode’s broader theme is adaptation—sometimes as a defense, sometimes as a weakness.
Notable Closing Point
The hosts end by noting that most people in the U.S. still don’t get enough fiber, tying back to their opening joke about beans and “fiber maxing.”