"Here’s a delightful morning snack: When Pakistan experienced severe flooding last year, it had the unexpected and rather creepy-crawly side effect of driving millions upon millions of spiders to the trees, where they could escape the floodwater. Since the flooding lasted for such a long time, many trees became blanketed in thick layers of web.
But according to the UK government, which assisted in the flood release effort this may have actually had a positive health effect: On-the-ground reports suggest that there are fewer mosquitos than would have been expected after the influx of so much stagnant water. This, in turn, may have reduced the very real risk of malaria to local populations afflicted with flooding. The web-coated trees, however, remain scary-looking."
This information and the pictures were taken from http://www.geekosystem.com/spiderweb-trees-pakistan/