The probability of an Elf Bug evolving into a Little Minor Elf is very low, out of twenty or so Elf Bugs, maybe only two or three will evolve, and there's a high chance of evolution failure.
As for whether the probability of evolution is related to the transplantation of Cordyceps, Liszt is not clear.
There is no evidence to suggest a connection between the two.
When Jela was still a Thorn Bug, its Cordyceps were planted in Tulip Castle, and it was only after migrating to Fresh Flower Town that it began to evolve and successfully did so. Although the assistance of the Smoke Mission played a part, it at least shows that Cordyceps can still evolve successfully after relocation.
"Perhaps for Elf Bugs, the transplantation of Cordyceps is like... the Tri-Phase Force of the Rubber Bug triplets?" Liszt suddenly thought.