Parashat Vaeira describes the first six plagues that God brought upon Egypt, yet the meaning of the fourth plague, Arov (ערוב), remains ambiguous. Unlike the more straightforward plague names like Dam (דם, “blood”), Arov is variously translated as “wild beasts,” “swarms,” or even “flies,” reflecting its lexical ambiguity and limited biblical usage, appearing only nine times in total (Exod. 8:16–21 and Ps. 105:31, Ps. 78:45). The lack of contextual clues further complicates its interpretation.
The most well-known interpretation, based on Rashi’s commentary, defines Arov as wild beasts. This view originates from the Midrash Rabbah, where Rabbi Yehudah asserts that Arov is a mixture of wild animals. However, in this Midrash, Rabbi Nehemya argues that it refers to a swarm of insects, specifically wasps and mosquitoes. Although the Midrash ultimately supports Rabbi Yehudah’s view, many English Bible and Haggadah translations, such as the JPS and the Jerusalem Bible, continue to render Arov as “flies” or “swarms,” aligning with Rabbi Nehemya's interpretation. Their reasons pre-date the Midrash Rabbah (and Rashi).
The translation of Arov into Greek in the Septuagint as kynomyíis (κυνομυίης, "dogflies") by Jewish scholars/ translators (at a time before the Midrash Rabbah) influenced later renderings. The Latin Vulgate rendered Arov as “muscis diversi generis” (different kinds of flies), leading nearly all non-Jewish translations to interpret the term as insects rather than beasts. This historical precedent has solidified the diverse translations we see today.