He sent divers sorts of flies ... - The account of this plague is found in Exodus 8:24. The word there used is simply “swarm,” without indicating what the swarm was composed of. The rabbis explain the word as denoting a mixture, or a conflux of noxious insects, as if the word were derived from ערב ‛ârab - “to mix.” The Septuagint renders it κυνόμνια kunomnia - “dog-fly” - which Philo describes as so named from its impudence. The common explanation of the word now is that it denotes a species of fly - the gad-fly - exceedingly troublesome to man and beast, and that it derives its name - ערב ‛ârôb - from the verb ערב ‛ârab, in one of its significations to suck, and hence, the allusion to sucking the blood of animals. The word occurs only in the following places, Exodus 8:21-22, Exodus 8:24, Exodus 8:29, Exodus 8:31, where it is rendered swarm, or swarms, and Psalms 105:31, where (as here) it is rendered divers sorts of flies.
And frogs which destroyed them - Exodus 8:6. The order in which the plagues occurred is not preserved in the account in the psalm.