Keep placing different combinations of logs and plants in the firepit until the message "The pungent smell makes the insects disperse" appears.
Tip: After receiving this message, it is helpful to record what stone corresponds to what plant.
An easy way to find the correct combination can be found in the following:
Start with the thermal bath. Figure out which plant out of the five is required to disperse the insects. Keep track of this plant.
Next, move to the mud bath to the east. One of the two plants will be the same as the last pool. Keep using a second plant out of the four remaining ones until the correct combination is discovered.
Move to the salt-water spring. Be sure to use the secondary plant from the last pool as the primary plant for this one. Keep trying combinations using the three remaining herbs until the correct one is found.
Now head to the sulphur spring. Use the new plant used for the salt-water spring as the primary plant for this spring. One of the two remaining herbs will be the secondary plant, so try them both.
Lastly, head to the Bandos pool. There are three plants required here, but players should have worked out what all the stones mean by now (there will be one new stone, but players should only have one unused herb).
After all of the bugs are taken care of, talk to Seegud.