The black light emitted by the Mother Gu was the notorious "Shadow Sand," which, during ancient times, could poison a person just by spraying onto their shadow.
The strength of the Qianji Gu lay not in the Shadow Sand, but in setting traps; however, its poison and hallucinogenic properties were also quite exceptional.
With Hua Hua's resilience akin to steel and iron, it could withstand a strike from it.
But it did not plan to withstand forcibly, because on Earth, this creature was called "Tianji Gu," known for its cunning schemes, which prompted it to timely slap on a Defense Talisman for itself.
The Mother Gu was once again dumbfounded: Fighting between Gu Insects, and you actually use a Defense Talisman... freaking hell, can you have some shame?
What about the dignity of a high-rank Gu Insect?