It is quite shocking to see this Jumping Spider (Menemerus sp.) holding on to a (Heteropoda sp.) Huntsman Spider's leg.
Could the Jumping Spider really take down the large Huntsman? Penney and Gabriel (2009) has recorded a Holcolaetis jumping spider feeding on a Huntsman spider. This is indeed a great feat. However, the jumping spider found by Penney and Gabriel is feeding on a whole huntsman spider by itself. This Menemerus that I photographed is only feeding on a leg.
I posted this earlier in the Arachnology page to see what others think about this. Scavenging behaviour is suggested. There is indeed a dead Heteropoda spider body around 30cm away which seems to be where this leg originated from. Scavenging in other spiders has been studied before but it is rare in Jumping Spiders as Jumping Spiders have a very developed eyesight (compared to other spiders) to identify their prey visually. Few studies has been done to show that some Salticids do scavenge, usually in spiderling or when live prey are scarce. Phidippus audax can even survive until adulthood as a scavenger. However, this behaviour is not studied in the tropical countries as preys are abundant. There needs to be more explanation than just scavenging for this Menemerus case as I wonder how did this happen. Did the Menemerus just found a dead huntsman and decided to pluck its leg out? or was the leg already seperated? Another thing that was unusual is the distance (around 30cm) this Menemerus carried the leg from the original body. Unfortunately the lab tests on scavenging behaviour did not measure how far a Salticid can carry its scavenged meal away.
The genus of this jumper may be able to give an important clue. Several species of Menemerus has been recorded snatching foods from ants (Jackson et al., 2008; Cushing, 2012). These spiders will approach ants that are carrying prey or brood and will sneakily snatch the load off the ants' mandibles with great accuracy and speed. I have seen this before and it is indeed one of the funniest behaviour I have ever observed in spiders. After snatching the food from the ant, it will quickly run away to a safe distance to enjoy its meal. This will leave the ants running around confused and agitated finding their load suddenly disappeared. This kleptoparasitism behaviour may explain how the spider got hold of a leg that has been carried away by ants from the Huntsman's body. One problem is that I did not notice any ants trying to dismember the Heteropoda's body.
There is one final hypotheses I would like to share. I have regularly observed Spider Wasps in this area dragging Heteropoda Spiders after injecting them with a paralyzing venom. While being paralyzed, the weakened struggling movement of the Huntsman's legs may cause this Jumper to misidentified it a caterpillar or a worm. After grabbing hold of the Huntsman's leg, autospasy causes the leg to break off.
These are the best answers I can think of. The best evidence to understanding this case is still the huntsman body itself. Unfortunately, I did not examine the Huntsman Spider body closely so I am unable to tell the cause of death. So this case will continue to be a mystery.
Everyone is welcome to add their opinions and explanation to this.
Menemerus = Jumper = Salticid = Jumping Spider
Heteropoda = Huntsman = Huntsman Spider
Kleptoparasitism = A parasitic behaviour where foods are taken from another animal
Autospasy = The breaking off / separation of an animal's limb from the weak areas due to being pulled
Cushing, P. E. 2012. Review Article Spider-Ant Associations: An Updated Review of Myrmecomorphy, Myrmecophily, and Myrmecophagy in Spiders. Psyche: 1-23.
Horner, N. V. and Starks, K. J. 1972. Bionomics of the Jumping Spider Metaphidippus galathea. Annals Of The Entomological Society Of America 65(3): 602-607.
Jackson, R. R., Salm, K., and Pollard, S. D. 2008. Short Communication: Snatching prey from the mandibles of ants, a feeding tactic adopted by East African jumping spiders. The Journal of Arachnology 36: 609-611.
Penney, D. and Gabriel, R. 2009. Short Communication: Feeding behavior of trunk-living jumping spiders (Salticidae) in a coastal primary forest in The Gambia. The Journal of Arachnology 37: 113–115.
Vickers, M. E., Robertson, M. W., Watson, C. R., and Wilcoxen, T. E. 2014. Scavenging throughout the life cycle of the jumping spider, Phidippus audax (Hentz) (Araneae: Salticidae). The Journal of Arachnology 42: 277–283.
Wolff, R. J. 1986. Scavenging By Jumping Spiders (Araneae: Salticidae). The Great Lakes Entomologist 19(2): 121-122.