杏吧原创

ON BAMBOO leaves in India, aphids fight over what may be the smallest
territories in the animal kingdom. William Foster of the University of Cambridge
has seen horned aphids, Astegopteryx minuta, duelling for possession of
tiny patches of leaf less than 50 micrometres across.

While birds and mammals often fight over territories, insects rarely do.
鈥淪mall animals on the whole don鈥檛 bother with territories,鈥� says Foster. 鈥淭hey
just reproduce as fast as they can and then die.鈥�

Yet the horned aphids, which are less than 1.5 millimetres long when
full-grown, appear to clash regularly over patches of leaf. Feeding aphids, with
their mouthparts sunk into a sap-bearing phloem vessel below the leaf surface,
are often attacked. The intruders use their 鈥渉orns鈥�, protruberences on their
heads, to try to lever the resident aphids away from the leaf鈥攍ike a
carpenter using a clawhammer to remove a nail. In response, the residents
perform headstands, bringing their full weight to bear on their opponents鈥�
heads.

Foster had suspected that the aphids might be fighting for possession of
large patches of leaf containing a rich supply of phloem vessels. But he found
that each time an intruder was victorious, it immediately sunk its mouthparts
into the tiny feeding hole left by its opponent (Animal Behaviour, vol
51, p 645). These holes were surrounded by a tiny raised collar of plant tissue
just 50 micrometres in diameter.

The aphids presumably have difficulty finding good feeding sites, which makes
securing a feeding hole by violence a viable alternative option.