My research revealed to me that the silithid are like bees; destroy the queen of the hive, and the rest of should be thrown into disarray. I'll brew a lure that we'll use to bring out the queen; once summoned, you'll take her down.
First though, we need some reagents; we don't want you bungling into the jungle unprepared. Go west to find the silithid hive in Un'Goro Crater and obtain a scent gland from one of the bugs. I'll also need some samples of the native Un'Goro soil.
Finding a suitable scent gland might take a bit - the gland can't be damaged, but the process of getting one certainly doesn't lend itself to it. As for the soil, I'd assume it should be easy enough to find.
Anyway, do you have the items I need to make the lure?