The names humans have for many of the flora and fauna of the Valley come from Rovari, the Daraz language (Daraz are native to the Valley, humans are not). This particular creature is called merev gombi in Rovari, which literally means “hard sphere.” Humans usually just call this animal “merev.”
Merev are the beast of burden of choice for this region. Opportunistic grazers, they’ll eat just about anything placed in front of them, making them extremely easy to maintain. They’re slow but sturdy, and nearly indestructible. When spooked, they don’t run: they pill. If you get into a spot of bother, you know your cart will be more or less where you left it.
The merev’s hide is too tough for many predators to pierce, and its center of gravity too low for them to knock it over. So most predators simply don’t bother with them. YOU might get eaten, but your pack animal won’t.
The merev is not an insect; it is yet another of the many monotreme species in the Valley.
Millenia ago, the people of the Valley domesticated an animal known as a cloud spider*. Spider silk is exceptionally lightweight and has extremely high tensile strength, and the humans have been able to tease many uses out of an animal that yields a large quantity of silk.
As humans have done with dogs, cows, etc., the people of the Valley have domesticated the cloud spider and bred multiple variations to suit specific needs. Mostly this is focused on producing different kinds of silk for different purposes, including varieties of silk that can be compacted, hardened, and moulded into all sorts of shapes. The resulting material is extremely durable, lightweight, and flexible. So in place of wood or metal, both of which are relatively scarce, most of their daily-use objects are made of silk.
So yes, the entire structure that houses the country of Pocalo and all its provinces is ONE GIANT SPIDER WEB that has been built up over the course of many thousands of years using construction-grade spider silk. Hence, if you are in any province but the very topmost, when you look up, your view of the sky consists mostly of silk. Hence the name “Valley of the Silk Sky.”
*Don’t worry, arachnophobes, it’s not actually technically a spider! It’s a MONOTREME. There are actual bugs in the Valley, but most of the larger incarnations like the cloud spider are really egg-laying mammals.
These creatures are a species known as the Daraz, and they are monotremes, a.k.a. egg-laying mammals. The Daraz come in four basic body types: Kiralyno (a.k.a. The Kira, the primary egg-layer); Hazastars (consorts to The Kira who are involved in reproduction); Munkas (non-reproducing laborers); and Harcos (non-reproducing warrior/hunters).
Of these, the only ones humans are ever likely to see are the Harcos, as the rest typically stay underground for most of their lives.
Your body type, and therefore your caste, is preselected at egg-laying based on what the clan needs most. Every egg has the potential to be any body type. Which one it grows into is determined mostly by what the embryo is fed while it is developing in the cell. Some will get a diet rich in thus and such hormone, and become breeding adults. Others will get a different hormone, and become non-breeding workers.
Daraz society is collectivist – you have a job to do for the good of the clan as a whole, and there’s not much room to decide you want to do something else. After all, if you’re a non-breeding worker caste, you do not have a reproductive system (beyond some vestigial internal organs). You can’t decide you want to be a breeding adult instead. If you are a Harcos your body is literally a weapon, and you will be expected to train in how to use it so you don’t hurt those around you just by existing.
Keverek
Ah, but biology is complex and prone to unpredictable variation, and as such this predetermination process doesn’t work smoothly 100% of the time. Up until about 6 weeks of gestation you can switch production over to a different body type without noticeable consequence. After a somewhat vague cutoff point, though, you wind up with someone who is a little bit this and a little bit that. These Daraz are known as “Keverek,” a.k.a. “mixed.” In these cases, you’re assigned to the caste you seem most similar to, and everyone just sort of hopes it works out.
Hali is one of these Keverek. Xe started out on the path to being a Hazastar, but a sudden need for more Harcos had xer production shifted fairly late in the game. Since Hazastars are significantly smaller and less muscular than warrior/hunters, Hali is shorter and thinner than xer compatriots. (Xe is also much younger than the other two in the illustration, who are adults tasked with training the up-and-comers.) Given that xe has all the Harcos weaponry and no evidence of a functional reproductive system, xe was assigned to the Harcos caste, and off to training xe goes.
The names humans have for many of the flora and fauna of the Valley come from Rovari, the Daraz language (Daraz are native to the Valley, humans are not). This particular creature is called merev gombi in Rovari, which literally means “hard sphere.” Humans usually just call this animal “merev.” 
Millenia ago, the people of the Valley domesticated an animal known as a cloud spider*. Spider silk is exceptionally lightweight and has extremely high tensile strength, and the humans have been able to tease many uses out of an animal that yields a large quantity of silk. 