If you apply this card's effect and send a Normal Monster to the Graveyard, you can then apply the additional effect that Special Summons monsters with the same name from your hand, Deck, and/or Graveyard.[1]
Even if you send a Normal Monster to the Graveyard, you can choose not to apply the addition effect that Special Summons monsters.[1]
Reducing battle damage to 0 and sending a Level 4 or lower Insect-Type monster to the Graveyard happen simultaneously, but Special Summoning monsters with the same name as the sent monster from your hand, Deck, and/or Graveyard does not happen simultaneously with those effects.[1]
The effect of this card that Special Summons an Insect-Type Normal Monster from your Graveyard when a monster on your field is sent to the Graveyard by an opponent's card effect starts a Chain. (This effect does not target, and cannot be activated during the Damage Step.)[1]
Q&A Rulings
Q: "Giant Ballpark" is face-up in my Field Zone. If my Insect Knight attacks my opponent's Mad Dog of Darkness, can I activate the first effect of "Giant Ballpark" during damage calculation?
A: In this scenario, Insect Knight and Mad Dog of Darkness both have 1900 ATK, so it is not a situation in which a player would take battle damage. Therefore, you cannot activate the effect of "Giant Ballpark" during damage calculation.[2]
Q: "Giant Ballpark" is face-up in my Field Zone, and an "Embodiment of Apophis" treated as a monster by its own effect is face-up in my Monster Zone. In this situation, if "Embodiment of Apophis" is destroyed and sent to the Graveyard by the effect of my opponent's "Raigeki Break", can I activate the second effect of "Giant Ballpark" that Special Summons an Insect-Type Normal Monster from my Graveyard?
A: As in this scenario, if a Trap Card treated as a monster is destroyed by an opponent's card effect and sent to the Graveyard, you cannot activate the second effect of "Giant Ballpark".[3]
Q: "Giant Ballpark" is face-up in my Field Zone. In this situation, if an "Inzektor Giga-Mantis" treated as an Equip Card is destroyed and sent to the Graveyard by the effect of my opponent's "Mystical Space Typhoon", can I activate the second effect of "Giant Ballpark" that Special Summons an Insect-Type Normal Monster from my Graveyard?
A: As in this scenario, if a monster treated as an Equip Card is destroyed by an opponent's card effect and sent to the Graveyard, you cannot activate the second effect of "Giant Ballpark".[4]