Further pleas to Pharaoh...
Flies come as a challenge to Uatchit, cattle a challenge Hathor and Boils a challenge to Sekhmet. Again Pharaoh is warned, gives no concession until the plague was upon them. Goshen, in v22 of chapter 8 (where the Isrealites lived) was separated and did not experience these plagues. This shows Pharaoh, Egypt and Israel that God can distinguish between them. The 5th plague was also warned, the 6th came with out warning - again Pharaoh has chances to change his hardened heart but chooses bitter instead of better. Pharaoh in chapter 5 v2 asks "who is the Lord that I should obey him?" so far 6 opportunities to change have presented themselves to Pharaoh but none are taken. By now I think he is knowing who the Lord is...obeying Him though will never happen with a hard heart.