Symbiotic Relationship between Spider and Fly
The archetypal example of a predator prey relationship is the spider and the fly, the idea of these two creatures being in a relationship that didn’t involve eating or being eaten would be farfetched to say the least, and yet this is what I observed.
I spotted Artabrus erythrocephalus, a medium sized Saltycidae jumping spider on a leaf at shoulder height. I moved in for some images and soon noticed the fly underneath the spider. Naturally I assumed that this Diptera was dinner for the spider, up until the moment when the spider moved.
The fly appeared to move with the spider. I encouraged the spider to move again and took a closer look, and sure enough, the fly was not being consumed, but was hiding underneath the spider.
At one point, the spider transferred to the underside of the leaf and the fly still managed to follow, and back to the top of the leaf. I captured a series of images, but with my poor eyesight, I had no clue as to what was going on.
I continued to observe, but my disturbance caused the spider to jump to an adjacent leaf. The fly followed, landing in front of the spider. The arachnid raised her front legs, and I truly thought the fly was toast, but then the legs lowered and the fly once again, took its position under the spider.
Obviously symbiotic, but at the time, I could not figure out what the spider got out of the relationship. A few weeks after the shoot, I zoomed in and noticed that the fly appeared to be feeding off the spider. Further research revealed that Nephila has been known to allow a fly to clean its fangs after feeding, then, it all fell into place. The fly was cleaning the fangs and around the mouth of the spider after a meal.
The fly was probably a Milichid, which are known for kleptoparasite behavior.
As far as I know, this particular relationship has not been photographed and extensive searches did not bring up any images of such scenes as this, so I do believe these images are unique.
Location is Bandung, West Java, Indonesia. Alongside a stream and paddy fields.