How could Hashem bring the creature known as the 'yidoni' agsainst the Egyptians?
(8,17) “For if you do not let My people go, behold, I will send against you and your servants and your people and in your houses a mixture of noxious creatures, and the houses of Egypt will be filled with the mixture of noxious creatures, as well as the land which they are upon it.”
The last phrase of this posuk, “as well as the land which they are upon it”, needs to be explained, and indeed we can explain it according to Rashi’s explanation that this plague consisted of every type of noxious creature, and the Mishnah in Kilayim 8:5 talks about a noxious creature called yidoni, and half of it is tied to the ground by a cord, and if this cord is broken it immediately dies.
Now, our posuk says that “the house of Egypt will be filled with a mixture of noxious creatures”, that is, every type of noxious creature. If so, we have to wonder how Hashem could bring against them also this yidoni, since it is attached to the ground by a cord which cannot be severed without killing it. Therefore, the posuk says “as well as the land which they are upon it”, referring to the land upon which this yidoni is attached, and by this method even this creature could be brought there alive.
What does the posuk mean “this time I will send all My plagues”?
(9,14) “Because this time I will send all My plagues into your heart.”
We can explain that Hashem has three legions which He uses to punish those who transgress his will, and these are fire, wind and water. With Sodom fire was used, water was used with the flood, and to punish those who made the tower of Babel wind was used, to scatter them upon the face of the earth.
And in Egypt all of them were used. The plagues of blood and frogs were with water, the plague of locusts was with the wind, as it says “and Hashem brought an east wind”, and the plague of boils was enacted using fire, as it says in Shemos 9:8 “take for yourselves handfuls of soot from the furnace”. But with the plague of hail all three of them were used together: the hail itself was water, and there was “fire flaming within the hail”, and there was also thunder which was with the wind. Thus it says here by the plague of hail, “this time I will send all My plagues”.