In article , wykehill-
says...
Today, I observed the water boatmen in our small garden pond raft up in a
kind of star shape. I have never seen this behaviour before, and I wonder if
anyone could explain it to me?
Here is a photo. The actual insects are about one centimetre long.

http://community.webshots.com/photo/...60022413uWvwBn


two guesses...1 a female has released a pheromone that attracted a mass
of suitors in which one will begin mating..or two under the mass is a
large insect/dead fish they are mass feeding on, but I don't think I
have heard of adults doing that where as the first couple of instars
will. Here is a page of a guy who probably could answer your question
better...scroll down the page to get his email.
http://www.ebc.uu.se/zooeko/GoranA/GA1.html
--
Lar

It is said that the early bird gets the worm,
but it is the second mouse that gets the cheese.