"Death of a Naturalist": Heaney uses the word ‘Death’ to suggest a metaphorical death of the speaker’s innocence. This could also represent that it is lost forever and they cannot get it back.
"festered in the heart": The word ‘heart’ suggests that it is a central place in the 'townland' and shows the importance of the flax-dam to the speaker.
"festered in the heart" and "Flax had rotted there,": The verbs ‘festered’ and ‘rotted’ could suggest that the flax is decaying just like his childhood innocence.
"the punishing sun": Heaney uses personification of the sun by using the word ‘punishing’. This could suggest that summer is relentless and harsh.
"Bubbles gargled delicately,": The adverb ‘delicately’ is a strange word to use to describe this disgusting scene. This shows the speaker’s appreciation for the flax-dam.
"But best of all": emphasises his youthful fascination.
"jampotfuls of the jellied specks" and "warm thick slobber": The words ‘slobber’ and ‘Jampotfuls’ suggests that the speaker in the poem is
young.
"wait and watch": The verbs ‘wait’ and ‘watch’ suggests that the speaker is excited and impatient.
"Miss Walls would tell us how": This vivid memory suggests that he is enthusiastic about the lesson regarding the frogs.
"For they were yellow in the sun and brown": The speaker in the poem has learnt facts about the frogs.
"Then one hot day when fields were rank": The 2nd stanza has a
change in tone. The word ‘Then’ suggests that the speaker in the poem changes his views.
"angry frogs": The adjective ‘angry’ to describe the frogs suggests that the speaker in the poem is aware of the dangers.
"Invaded" , "cocked" , and "mud grenades": the reference of war in the poem may indicate that the speaker has a war with the frogs.
"I sickened, turned, and ran.": This is a direct contrast to his enthusiasm and passion in the beginning. Metaphorically, he has now lost his innocence and can see the dangers in the world.
"great slime kings": ‘king’ implies that the frogs now rule the flax-dam and that he is not wanted there.
The adjective 'great' suggests that they hold all the power.
"spawn would clutch it.": The verb ‘clutch’ suggests that he is now afraid and scared of the frogs. He believes he will not be able to escape from the knowledge of how he views the ‘angry frogs.’ Again, this is a metaphor for his loss of innocence.