Nathaniel's friend is exhibiting behaviors that suggest a loss of grip on reality and a possible hallucination, as he believes he is being attacked by fireflies and is responding with aggression. The type of drug that most closely aligns with these symptoms is a hallucinogen.
Hallucinogens can cause individuals to perceive things that are not present (hallucinations) and can lead to aggressive behaviors. Therefore, the correct answer is:
• hallucinogen