To address the point you raised, I generally treat line weight as being part of the core construction, just clarifying it. Adding texture is a whole different thing, however, and introduces additional goals of what you're communicating to the viewer, rather than just clarifying what has already been communicated.

Starting with your organic forms with contour curves, your work there is looking solid. The sausages are nice and simple, and the contour curves do a great job of making those forms feel solid as individual, three dimensional entities.

Continuing onto your insect constructions, for the most part you've done a really good job in constructing complex objects/creatures from a series of simple forms, and as a whole you're doing a good job of establishing the illusion that each structure is three dimensional. There are however some habits/approaches that I'd like to warn you away from in the future.

The first issue I wanted to point out was that you have a tendency to be just a little loose with your linework. It's not to say you're not thinking about where your lines are going, but rather that I can see instances here and there where you put down multiple marks where one executed properly with the ghosting method should suffice. I'm also not talking about the use of line weight, which is something that is added once the forms in question have already been constructed - I'm talking about a more habitual, automatic execution of multiple marks, in the place of just one.

Remember that what we're doing here is not sketching. We're drawing with a sense of purpose, planning each and every mark before executing it, through appropriate use of the ghosting method.

The second thing I wanted to address is something we can see in two locations in this hornet image, both in its abdomen and its thorax, albeit in two different ways (making this image very useful to this point).

Starting with the abdomen, you laid it in with a simple ball form, but when you then went onto 'refine' the form, you basically redrew the entire silhouette over the solid ball form that was already present. This basically tells the viewer that there are two independent forms occupying the same space, and leaves them to sort out what that's supposed to signify (usually creating a contradiction that undermines the viewer's suspension of disbelief altogether). You can see this explained in these notes, as well as in this demo involving a crab's claw.

On the thorax, however, we can see that you started out with this basic ball form there, and you ended up taking the silhouette of that ball form and modifying it, extending it upwards to make it a little bigger.

Both of these approaches are incorrect for the same reason - they involve treating your drawing as though it is just a bunch of flat shapes and lines on a flat page, and modifying them to try and create the result you want. Unfortunately, construction is all about accepting and respecting the fact that what you're doing is not drawing a bunch of shapes - I mean, it is, but we're basically giving way to complete insanity and delusion in order to convince ourselves, and by extension others, of something that simply isn't true. That is to say, what we're trying to give the impression of is that we're creating a bunch of solid 3D forms in a 3D world and mashing them together to create more complex objects. The second we stray from this hallucination and go back to treating the drawing like it's just lines on a page, is when we undermine the illusion.

So, whenever you see a silhouette of a 3D form and decide that you're just going to make some small change or tweak to it, know that what you're doing is not going to make a believable 3D result. Instead, it's like we're looking at the footprint in the mud of some animal. Despite not having seen the animal, there's a lot we can tell from its footprint. If however we were to change its footprint, we wouldn't be changing the animal that created it - we'd just be making that footprint less useful. The same thing can be said of modifying the silhouette of a 3D form.

The only way to interact with our constructions, therefore, is through the addition and manipulation of forms in 3D space. In this case, it'd be through adding more solid, 3D forms that wrap around the existing structure.

Moving on from that point, I noticed that you seem to have employed a lot of different strategies for capturing the legs of your insects. It's not uncommon for students to be aware of the sausage method as introduced here, but to decide that the legs they're looking at don't actually seem to look like a chain of sausages, so they use some other strategy. The key to keep in mind here is that the sausage method is not about capturing the legs precisely as they are - it is about laying in a base structure or armature that captures both the solidity and the gestural flow of a limb in equal measure, where the majority of other techniques lean too far to one side, either looking solid and stiff or gestural but flat. Once in place, we can then build on top of this base structure with more additional forms as shown here, here, and even here in the context of a dog's leg (because this technique is still to be used throughout the next lesson as well). Just make sure you start out with the sausages, precisely as the steps are laid out in that diagram - don't throw the technique out just because it doesn't immediately look like what you're trying to construct.

Lastly, a minor point about detail. I can see a number of places where you've gone from just communicating the textural qualities of a surface to the viewer (capturing what it might be like to run one's fingers around the various surfaces of the object), to just focusing on decorative rendering. For example, we can see along the abdomen of the hornet I linked previously, and we also see it on this weevil where you've just captured subtle shading. In the future, leave that out of your drawing, and remember the principles laid out here from Lesson 2.

Anyway, I'm still very pleased with your results, and I am happy to mark this lesson as complete. Be sure to keep what I've mentioned here in mind, and apply it in the next lesson.