Abstract
BackgroundUpon the detection of imminent peril, pea aphids (Acyrthosiphon pisum) often drop off their host plant. Dropping in response to insect enemies is intermittent in nature, but when a mammalian herbivore feeds on their host plant, a large mixed-age group of aphids usually drops off the plant at once. Aphids that reach the ground are confronted with new, hostile environmental conditions and must therefore quickly walk toward a suitable host plant. The longer it takes an aphid to reach a host plant, the more it is exposed to the risks of starvation, desiccation and predation.ResultsWe found that young nymphs, which have limited mobility and high mortality on the ground, quickly climb on conspecific (not necessarily parental) adults and cling to them before the latter start walking in search of a plant. This “riding” behavior is likely to be adaptive for the nymphs, for it shortens their journey and the time they spend off a host plant. Adults however, seem to be irritated by the riding nymphs, as they often actively try to remove them.ConclusionsAfter dropping from the host plant, young aphid nymphs travel at least part of the way back to a plant on the backs of adults. For the riding behavior to take place, nymphs need to successfully find adults and withstand removal attempts.
Highlights
Upon the detection of imminent peril, pea aphids (Acyrthosiphon pisum) often drop off their host plant
Dropping is an efficient way of evading an approaching enemy, but it comes with a cost: an aphid that reaches the ground is challenged by the need to return to the original host plant or find a new one, before it starves to death, becomes desiccated or falls prey to ground-dwelling predators [5, 6]
We initially described and quantified this new “piggybacking” behavior ( “riding”) and tested the hypothesis that riding creates an intergenerational conflict, i.e. the nymphs initiate it, improving their chances of reaching a host plant, while the adults try to avoid it as it is a burden for them
Summary
Upon the detection of imminent peril, pea aphids (Acyrthosiphon pisum) often drop off their host plant. Dropping is an efficient way of evading an approaching enemy, but it comes with a cost: an aphid that reaches the ground is challenged by the need to return to the original host plant or find a new one, before it starves to death, becomes desiccated or falls prey to ground-dwelling predators [5, 6]. Despite these risks, the pea aphid (Acyrthosiphon pisum) often drops
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