As a whole, I think you've done a pretty good job in this lesson. There are a handful of things I want to call out, that I believe will help you solidify your grasp of what exactly we're doing here, and how to get the most out of these exercises, but you're kind of at that point where you seem to have an underlying understanding of it, but it's not entirely solidified. And so, while most of the time you're demonstrating that grasp, there are little slip-ups here and there that suggest that the grasp itself is still subconscious, and not fully intentional all the time.

Before we get into that, I do want to address what you mentioned about your moth, just so I don't forget to do so later. Given the relatively light touch on texture elsewhere in the construction, mainly focusing on the areas of fur (which is totally valid), one could argue that just focusing on the overall footprint of the antennae and leaving the individual hairs out would have been fine. That said, you could certainly approach this more as a texture, or alternatively, as a complex leaf-type structure from Lesson 3 (though you're right, this would result in a lot of noise). Each of these approaches are tools for you to employ, and it is the situation as well as your intent that determines which is the correct choice. Consistency, however, across the drawing as a whole, is probably the main thing you want to focus on.

Getting into your actual critique - to start, I can see that you're clearly trying to focus on the characteristics of simple sausages in your organic forms with contour curves, albeit there is definitely room for improvement here. Specifically, there's a tendency to let the midsection get a touch wider, and for the ends to become more stretched out (rather than remaining entirely circular in shape), but all in all these are moving in the right direction, and I am pleased with the confidence of the stroke. These shapes will improve with practice, but what is most notable to me is that the intent is clear. Also, this does steadily improve even from the first page to the second.

As to the contour curves themselves, these are looking good - they're confidently executed, smooth and even in shape, and I'm pleased to see an awareness of how the degree shifts wider as we move farther away from the viewer.

Moving onto your insect constructions, the first thing I want to talk about is the importance of understanding the difference between working in 3D space - with an awareness of how we're actually adding three dimensional forms to a three dimensional structure - and working in 2D space where we're just putting lines down on a page, and engaging with a flat drawing. As I've already mentioned, there are a ton of ways in which you're demonstrating an underlying grasp of this, but there are some areas where you take little shortcuts in 2D, little liberties, where I think we can really establish what that difference is for you more concretely, as well as the benefits of sticking to 3D at all times.

Because we're drawing on a flat piece of paper, we have a lot of freedom to make whatever marks we choose - it just so happens that the majority of those marks will contradict the illusion you're trying to create and remind the viewer that they're just looking at a series of lines on a flat piece of paper. In order to avoid this and stick only to the marks that reinforce the illusion we're creating, we can force ourselves to adhere to certain rules as we build up our constructions. Rules that respect the solidity of our construction.

For example - once you've put a form down on the page, do not attempt to alter its silhouette. Its silhouette is just a shape on the page which represents the form we're drawing, but its connection to that form is entirely based on its current shape. If you change that shape, you won't alter the form it represents - you'll just break the connection, leaving yourself with a flat shape. We can see this most easily in this example of what happens when we cut back into the silhouette of a form.

While I basically haven't seen any specific instances of that kind of "cutting into silhouettes" issue in your work, I did find a number of instances of extending or adding onto existing silhouettes/3D structure with either flat shapes, or individual marks that would enclose those shapes against the structure. Since that sentence is probably confusing as hell, here's what I mean on your monkeyhopper construction.

Instead, whenever we want to build upon our construction or change something, we can do so by introducing new 3D forms to the structure, and by establishing how those forms either connect or relate to what's already present in our 3D scene. We can do this either by defining the intersection between them with contour lines (like in lesson 2's form intersections exercise), or by wrapping the silhouette of the new form around the existing structure as shown here.

The way you approached part of the monkeyhopper's head with a box is definitely thinking in the right direction - I wouldn't necessarily use something quite as geometric in an organic construction, but it's definitely the right thinking all the same. You can see this in practice in this beetle horn demo, as well as in this ant head demo (which should provide an alternative approach to thinking through that monkeyhopper's head construction).

This whole premise is something I've been pushing more recently - so while it isn't as clearly represented in the lesson material yet (something I'm gradually updating, one step at a time), but you'll also find that the shrimp and lobster demos on the informal demos page demonstrate this as well.

Note in particular how every stage focuses on establishing the forms as solid and three dimensional before moving onto the next. This is all part of accepting that everything we draw is 3D, and therefore needs to be treated as such in order for the viewer to believe in that lie.

Continuing on from there, I did notice some issues with your leg constructions - you mentioned that you're having trouble with the sausage structures, which is totally normal (especially as we get into skinnier structures), but there are some spots where I noticed you "drawing through" your sausages in the manner we do ellipses. The thing is, we do that for ellipses because it actually allows us to lean more into the arm's natural desire to draw ellipses - and so if you do that for a sausage, it's going to become more ellipse-like, and deviate from the specific characteristics outlined in the sausage method diagram.

Ultimately 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.

From there, we can build upon that structure (as I noticed you doing yourself, although more in two dimensions). We can instead build on top of this base structure with more additional, complete, three dimensional forms as shown here, here, in this ant leg, 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).

So! With all that laid out, I'll go ahead and mark this lesson as complete. You can continue to explore and address the points I've raised here as you move into the next lesson, where it all continues to be equally relevant.