I don't recommend ethyl acetate.  You really need to leave the insects in
the jar for 8 hours or more to assure complete death, at least for hardier
specimens.  (Dragonflies are the worst, and tend to mess themselves up
long before the ethyl acetate knocks them down.)
 
I haven't found anything that beats cyanide, unfortunately.  It's rasty,
but it does the job, probably because it's so lethal--same qualities that
make us all nervous.
 
Good luck on a substitute.
 
 --Jane Beckman