Subject: Dragonfly mouth secretions

We recently had a dragonfly alight on a clothesline outside our 
window.  It sat there for several hours and slowly secreted a black 
tarlike glob from its mouth onto the clothesline, then flew off.  The 
gummy secretion solidified and remained on the rope for a long period 
of time.  What was the dragonfly doing?

Re: Dragonfly mouth secretions