Albert Barnes Commentary Psalms 78:45

"He sent among them swarms of flies, which devoured them; And frogs, which destroyed them." — Psalms 78:45 (ASV)

He sent various 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 κυνόμνιαkunomnia - “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 various 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.