Players be like
I don’t really know d&d well, but I just looked up the spell and I think it says you can transform “any number of willing creatures”. So the DM could make an argument about whether insects had the intelligence to even qualify as being able to be “willing” for that.
On the other hand, I am a big fan of Operation Dumbo Drop Multistrike
https://www.dndbeyond.com/spells/1995-animal-shapes
Another problem might be that animal shapes only has a range of 30 ft
30 ft range, requires willing creatures, targets can become large or smaller (elephants are huge)…
Fine fuck horse storm it is
Brown Bear Barrage.
Or Giant Scorpion Tsunami if you want maximum pants-shitting potential.
(I could only find one CR4 large beast, the giant coral snake from Curse of Strahd, but no good spell title came to mind.)