There is hadith that says that the flies life span is 40 days and that it is in hellمث " عمر الذباب أربعون ليلة والذباب كله فى النار إلا النحلة" The question comes on the lifespan of fly As modern science states that fly lifespan is between 15 to 28 How do we reconcile this

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

The Hadeeth that reads: “All flies are in the Fire, except for the bee.”, was reported by al-Bazzaar and at-Tabaraani, and al-Albaani classified it as Saheeh (authentic).

As for the Hadeeth that reads: “The life span of flies is forty nights”; it was reported by Abu Ya’la from the Hadeeth of Anas, may Allah be pleased with him.

Ibn Hajar said: “Its chain of narrators is good.”

But it was only narrated by Sekkeen Ibn Abdul-‘Azeez about whom an-Nasaa’i said: “He is not strong.”

Then Ibn al-Jawzi mentioned it in his book al-Mawdhoo’aat [i.e. the fabricated Ahadeeth].

It appears –Allah knows best –that this Hadeeth is not confirmed.

If we presume that it is confirmed, then it is said that forty days is its maximum life-span. Otherwise, it may die before that, as stated by az-Zarqaani in Sharh al-Mawaahib al-Laduniyyah.

On the other hand, what is meant by the fly in the Hadeeth is more general than the domestic fly whose life-span is mentioned. Rather, it is more general than that.

Lisaan al-Arab reads:

“Black flies that are in the houses, fall into pots and food. Flies also refer to bees.”

Allah knows best.