Bulugh al-Maram 14
and Abu Da’ud who added:
“It (the fly) protects itself with the diseased wing (by dipping it first in a drink).
وَأَبُو دَاوُدَ, وَزَادَ: { وَإِنَّهُ يَتَّقِي بِجَنَاحِهِ اَلَّذِي فِيهِ اَلدَّاءُ }   1‏ .‏‏1 ‏- سنن أبي داود (3844)‏ وإسنادها حسن.‏