Young aphids avoid erroneous dropping when evading mammalian herbivores by combining input from two sensory...

Area of Science:

• Ecology
• Animal Behavior
• Insect Physiology

Background:

• Mammalian herbivores can accidentally consume insects, like pea aphids (Acyrthosiphon pisum), while feeding on plants.
• Adult pea aphids drop from host plants in response to simulated herbivore cues (breath, vibrations) to avoid predation.
• Aphid nymphs also drop to escape threats but face higher risks due to slower mobility and lower chances of finding new host plants.

Purpose of the Study:

• To investigate age-specific differences in pea aphid (Acyrthosiphon pisum) responses to simulated mammalian herbivore cues.
• To test the hypothesis that nymphs interpret herbivore cues more conservatively due to higher ground-related risks.

Main Methods:

• Exposed adult and first-instar nymph pea aphids to varying combinations of simulated mammalian breath and vibrations.
• Quantified and compared the dropping rates of nymphs and adults across different stimulus conditions.

Main Results:

• Adult pea aphids predominantly dropped in response to simulated breath alone.
• Nymphs rarely dropped to breath alone, but their dropping rates significantly increased with concurrent vibrational stimuli.
• Nymphs showed a threefold increase in dropping with one vibration and a sixfold increase with two vibrations accompanying the breath stimulus.

Conclusions:

• The age-specific escape responses of pea aphids are adaptations to the differential costs of dropping for adults and nymphs.
• Vulnerable nymphs utilize a multi-modal sensory integration strategy to avoid costly mistakes when detecting potential mammalian herbivores.
• Mammalian herbivory exerts a direct trophic effect on plant-dwelling insects, influencing their defensive behaviors.