Also, make sure Jaheira has cast some defensive spells on herself beforehand, and let a mage cast some protection on her. Then, when she is transported to the pit she at least has her protections on (use Iron Skins for example)
And I think Memnoch is right and you are using Summon Insects. Insect Plague is 5th level, Summon Insects 3rd level.
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Melusine, High Queen of Fluffies, Archbabe of the OHF, the LH,
the HADB and the SPAE(Society for the
Prevention of Acronym Extinction) &
Official Entertainer Elf of the BG2 Bar
Your voice is ambrosia