From Shadows

The drop rate for the Kaheti Swarm Chitin is absolutely abysmal. I submitted a suggestion to reduce the number required for this quest down to 2. I've been killing the Noth Venomsprayers and Drones Invasive Nothwings in Azj-Kahet for over an hour and have only skinned 4 of them, including using two Elusive Creature Baits.

I'm not sure if it's bugged or not, but if you're trying to skin these on your own, either be super invested in the tree that improves your chances at getting species-specific drops, or be prepared to spend a really long time trying to get to 5.

Edit: Drones are unlootable/unskinnable mobs. I meant to say Invasive Nothwings.

Some of these drop from lured enemies, the special "elusive" versions.

Enh, that's not "I found some mobs". The "Elusive" creatures are summoned by players using an item with a 12-hour cooldown.