Duelling aphids: electrical penetration graphs reveal the value of fighting for a feeding site.

Horned aphids (Cerataphidini) fight each other for access to feeding sites on leaves. An attacker attempts to force another aphid to abandon its feeding site; the victor then appears to insert its stylets into the site relinquished by the loser. This study used electrical penetration graph (EPG) recordings of Astegopteryx pallida (Van der Goot) individuals to pinpoint the benefits of fighting. We show that victors take significantly less time to commence feeding in the phloem, measured from the start of probing with their stylets, compared with aphids that initiate a new or discover an abandoned site: 9.0 versus 22.9 min, respectively. We also recorded the behaviour of aphids unencumbered with the wire necessary for EPG recordings. Those adult aphids that acquired a feeding site through fighting commenced feeding on average 20 min earlier than those that did not, taking into account the time spent searching and fighting as well as probing. This study clearly establishes that horned aphids use the exact feeding site vacated by another individual and that the benefit they gain is rapid access to the phloem - more rapid, indeed, than has previously been recorded in any aphid.