Jackson & Cross, 2011 figure 3
caption:
‘Portia labiata (left) from the Philippines stalking a spitting spider, Scytodes pallida (right).
Approaching head on would bring Portia into Scytodes’ line of fire. Instead,
Portia executes a planned detour by which it approaches this dangerous prey from the rear.’
‘Distances between Portia and the surrounding array are too far for
Portia to cross simply by leaping. The only way Portia can reach its
prey is to walk down to the floor and over to one of the two poles,
climb it and then follow the path to the prey. However, once on the
floor, Portia can no longer see the prey.’
‘P. labiata foregoes the detour and instead takes the shorter, faster head-on approach when the spider it sees in a web is a Scytodes female that is carrying eggs (Li and Jackson, 2003). This makes sense because Scytodes females carry their eggs around in their mouths. Egg-carrying females can still spit, but only by first releasing their eggs (Li et al., 1999). Being reluctant to release their eggs, egg-carrying females are, for P. labiata, less dangerous as prey.’
But is this prey-specific activity really evidence of planning? No!
Jackson & Cross, 2011 figure 2
caption:
‘Apparatus used for testing Portia fimbriata’s detour-planning
ability. Portia was on top of the central pole before each test
began. The prey item (lure made by mounting a dead spider in
life-like posture on a cork disc) (not shown) was on one of the two
ramps (whether on the left or the right ramp decided at random).
Portia viewed the prey while on top of the central pole but could not
see the prey when it went down the pole. By consistently taking the
route that leads to the prey, Portia demonstrates ability to plan
ahead.’
‘P. labiata foregoes the detour and instead takes the shorter, faster head-on approach when the spider it sees in a web is a Scytodes female that is carrying eggs (Li and Jackson, 2003). This makes sense because Scytodes females carry their eggs around in their mouths. Egg-carrying females can still spit, but only by first releasing their eggs (Li et al., 1999). Being reluctant to release their eggs, egg-carrying females are, for P. labiata, less dangerous as prey.’
‘Portia’s task always came down to choosing which one of two paths
would lead to the prey. Sometimes Portia had to walk past the wrong
pole before reaching the correct pole, and sometimes Portia had to
head directly away from the prey before accessing the correct pole.
Yet, regardless of the details and despite having no prior experi-
ence of taking or even seeing the paths available in the experiments,
Portia chose the correct pole significantly more often than the wrong
pole.’
