17. For if you do not let My people go, behold, I will incite against you and against your servants and against 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 upon which they are.
יז. כִּי אִם אֵינְךָ מְשַׁלֵּחַ אֶת עַמִּי הִנְנִי מַשְׁלִיחַ בְּךָ וּבַעֲבָדֶיךָ וּבְעַמְּךָ וּבְבָתֶּיךָ אֶת הֶעָרֹב וּמָלְאוּ בָּתֵּי מִצְרַיִם אֶת הֶעָרֹב וְגַם הָאֲדָמָה אֲשֶׁר הֵם עָלֶיהָ:
The following is a quote.
“ומלאו בתי מצרים את הערב וגם
האדמה אשר הם עליה”
“The houses of the Egyptians shall be full of the mixture of animals and also the ground upon which they are.” (8:17)
QUESTION: The words “and also the ground upon which they are” seem superfluous?
ANSWER: Among the animals of the world there is an extremely rare one found in the wild jungles of Africa and known as the “adnei hasadeh.” It has the face of a person, long hands that reach to its knees, and a very unusual relationship to its habitat. It is always connected to the ground through a string that comes out of its navel. Although it is very dangerous and kills anyone who comes within its reach, there is one way to capture it: Shooting arrows at the string which connects it to the ground. As soon as it becomes detached, it screams bitterly and dies immediately. Hashem brought upon the Egyptians a mixture of all the animals from the entire world, including the strange and vicious “adnei hasadeh.” In order that they not die before arriving in Egypt, they were brought together with the earth to which they were connected. Therefore, Moshe told Pharaoh, “The homes of the Egyptians shall be filled with the mixture of wild animals and also ‘adnei hasadeh’ will come, together with the ground (earth) upon which they are [attached]."
פנים יפות, ועי’ כלאים פ”ח מ”ה ברע”ב ותפארת ישראל
Sforno reads this passuk that the noxious creatures will be fill the houses and also the earth.
There are a number of mefarshim who notice that this extraneous descriptive phrase. "The earth on which they are", should modify the closer object and not the overall passuk and they suggest various answers.
(quoting the GR”A which is also summarized in Pardes Yosef)
(Avakesh adds: Netsiv explains that the plague of Arov starting from the Pharaoh's house and then involved his servants' houses and the houses of the other Egyptians. From there it spread into the land of Egypr - hence, "also the land on which they (the servants) live upon".)
This exotic animal, "Adnes Hasadeh", whose existence is not observed today is also contended historically:
However still other mefarshim (Midrash Yonason [Eibeshitz], Maharil Diskin, Panim Yafos http://www.dafyomi.co.il/bechoros/insites/be-dt-009.htm and http://www.dafyomi.co.il/parsha/vaera2.htm) offer the answer that the dirt from these animals’ homelands accompanied them so that they would be comfortable and confident why carrying out the plague according to HaShem’s will.
The Rogachover http://www.hebrewbooks.org/22177 p15 ( p.124 in pdf) (translated in Torah Tavlin 5765) concurs and also states that not only animals but also plants yield better produce when in their own earth. Also quoted online is a similar proposal to clarify the odd language of the passuk. http://www.ladaat.net/siteimages/fl_4f1814661e8b5.pdf
One wonders why an animal that is attached to the ground had to be invoked to explain this possuk when so many simpler answers are possible. Indeed, even the explanation that the animals had to be in their comfort zone to best carry out their mission is itself is out of the comfort zone of many people who hear it. Sometimes the literal reality is not to be taken literally!
Avakesh comments: Tiferes Yisrael on Kelayim thinks that Adnei Hasadeh is Orangutan. A number of sources are collected in Nathan Slifkin's, "Mysterious Creatures, p. 134-138. In his introduction, he also discusses various approaches to aaggados about animals that do not exist in our times and for which there is no evidence that they ever existed.