this is at some points far away from my original idea but it still stays true to them. the Zernag are a race of volcanic insects living in lavalakes and volcanos. they are very fast and although their hands look very thin and fragile they can easily crush rocks. the Zernags were feeding only on rocks in their early state of existence. the strong hands are a leftover from those days. their lower jaw can split into half this is also a leftover of those times. they use(d) it to hold stone to either crush or to shoot lava-like saliva out of their tongues at the stone. they can use their tongue so precisely that they began to forge weapons, tools and other stuff out of the ore that can be found in the areas they live. female and male Zernag look almost the same with little differences. the females have a thinner body and they have small holes in their chest. in those holes are almost transparent sacks that get filled with a nutritious juice when the Zernag is pregnant or in heat. the number of those holes depends on what status the Zernag has in the colony.
the second arm pair evolved into winglike fins so they can swim even faster and make quick movements in the lava.

fun fact: the body of a zernag becomes very soft during moments they are calm or during sexual acts. best time to make an suprise attack but who would want to kill them? xD please no hate comments. thank you (*imagines how many trolls wanna say "kill it with fire!" xD go ahead and try)