Alrighty! So all in all your work here is quite well done. You're employing the main principles from the lesson pretty well, specifically in how you're respecting the solidity of most of your forms and combining them together to create more complex objects. There are some places where you deviate from this a little bit (which I'll point out) and some other smaller issues that I'll identify, but generally you're demonstrating a good grasp of the concepts.

Starting with your organic forms with contour curves, these are pretty good. Try to avoid having them get narrower/pinch through their midsection and make sure they're the same size on both ends (which most of them are), and maybe put a little more time into applying the ghosting method to your curves (which includes rotating the page to find a comfortable angle of approach - I'm noticing certain orientations tend to be worse off than others).

I'm going to focus my critique on two of your drawings, as they serve as good examples of particular issues.

First off, your weevil. Here I've pointed out one major issue, and it's a big one. You don't have issue with it in most of your other drawings, but it's still a significant enough concern that it needs to be highlighted.

Basically constructional drawing is all about respecting the idea that every single form you draw is a solid, three dimensional addition to a three dimensional world. They're not shapes on a page, they are each of them solid masses, and we need to recognize and respect this throughout every step of our drawing. If you look at the area I highlighted near the weevil's spines, you can see how you constructed a ball form for the abdomen early on, and then cut back into its silhouette as you built up your construction.

The silhouette of a 3D form is not itself three dimensional - it is a flat, two dimensional shape that represents the form on the page. The nature of the 3D form is what determines the resulting silhouette shape, and so how we draw that silhouette will be determined by how we play with the form itself - but we cannot work this in reverse. We cannot change the silhouette to modify the form itself - what's done in 2D flat-world stays in 2D flat-world, and therefore reminds the viewer that what they're looking at is in fact just a flat drawing on a flat page.

Instead, we need to build things up by respecting the solidity of the forms we've drawn. You can see a really quick demonstration of this on the right side of my redlining for this drawing - basically you create a solid 3D ball, then you add cones to it, and finally you add additional masses that wrap around the base of the cones to create a smoother transition from the spines to the main mass. Each of these elements added, at every point, is itself a 3D form. Everything is drawn in its entirety, and the relationship between those forms are clearly established with intersection-style contour lines.

You can also read about this kind of issue here, where I explain how subtractive construction can be done incorrectly (as it has been done on this weevil). Generally speaking, you want to stick to additive construction when working with organic forms.

When it comes to the importance of defining the relationships between forms (via intersection lines/contour lines), you can see me doing this on the second drawing I wanted to draw your attention to your snippy snappy fucking garbage monster. I hate scorpions. As you can see on the claws, it's really important that you clearly define where one form intersects with another, how they connect, etc. We can do this by drawing a contour line that runs along the area where those two forms meet.

As far as this concerned, I actually have a specific informal demo talking about constructing claws additively which should help round out the whole additive/subtractive construiction thing, while applying to a snippy snappy shitlord (although this one's a crab, which is notably less offensive).

Another concern I point out against your scorpion is that it's important in many constructions, but especially in scorpions, to be aware of where the transition between the various major planes of a form occur. They're not generally as obvious or clear-cut as we might like (because they tend to be more gradual and rounded), but it helps to just put one down somewhere. This helps us understand the forms not just as vaguely continuous curves, and allows us to better grasp the symmetry of the construction and how any segmentation might wrap around them. Here I felt that you pushed your segmentation a little too far down the side, and I would have had them end right after the transition from top to side plane.

A couple more minor points - there needs to be more thought as to where exactly you place your contour lines. You appear to draw them a lot, basically as a sort of reflex whenever you feel things are not 3D enough. It's understandable, but the choices we make should all be the result of clear thinking, and no lines should be wasted. First off, contour lines placed at the joints between forms (as discussed previously) are extremely effective at making forms feel 3D - so for example, those used in the sausage method are critical.

You'll notice that I also mention in that diagram that you should not place other contour lines along the length of the sausage forms. This is because when the joint is reinforced correctly and the form itself is kept simple (two equally sized spheres connected by a tube of consistent width), no further contour lines are necessary. Contour lines themselves suffer from diminishing returns - one can do a lot, a second will do less, the third and fourth etc. will contribute virtually nothing, aside from cluttering the drawing. It's critical that every mark we draw is weighed and consider prior to execution - we need to think about what its job is, what it is meant to accomplish, whether it's the best choice to do it and whether or not there are other lines present already that attempt the same thing.

So! Aside from those points, I have just one minor thing to mention - on your coconut crab, you tried to add a little detail, but it appears to have been a bit of a rush job with a lot of more or less random lines drawn very quickly. I know you're eager to be able to whip things off with the kind of ease and swiftness you see from other artists, but remember that they've honed their instincts by first being more deliberate with every aspect of a drawing. In this case, it's important that every single mark you put down to imply the presence of textural forms be itself a closed and filled shadow shape - meaning, don't draw lines with separate start and end points, draw closed shapes first, then fill them in as shown here. And of course, don't draw a mark until you really know which specific form you're trying to imply the presence of. You may want to quickly revisit Lesson 2's section on texture, cast shadows, and implied vs explicit drawing techniques.

All in all, your constructions are largely well done. There are a few things to keep in mind, but I mainly just focused very heavily on specific issues that I saw in one or two places. As such, I'll go ahead and mark this lesson as complete.