First, not a good idea to post images here - best to do so on alt.binaries.pictures.gardens.
The insect is question is a fairly common creature, a dragon or damsel fly. Not sure what specific species, but they are found all over in areas with some sort of water feature - lakes, ponds, swamps, slow moving streams, even waterbowls, birbaths and other garden water attractions.
pam - gardengal