This biasing force will return the flap portion into contact with the base once {HEAD ~ an insect} has lifted {TAIL ~ the flap} to enter the trap 
lifted
This biasing force will return the flap portion into contact with the base once { HEAD ~ an insect } has lifted { TAIL ~ the flap } to enter the trap
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH