Starting with your organic forms, one major issue does come into play - you're skipping over the instructions on maintaining simple sausage forms. You've got a number of cases where the sausages get wider through their midsection, ends that are of different size, and ends that are stretched out. Always remember - every sausage should essentially be two equally sized spheres connected by a tube of consistent width. This simplicity will help maintain the illusion that they are solid, three dimensional forms, even without contour lines added to them.

Now, moving through your insect constructions, there is actually a lot of points of strength, and I get the overall impression that you are developing a good grasp of how forms interact with one another in 3D space. There are however a number of small issues that come together to undermine the solidity of your results. Similarly, there are places where you follow the instructions from the demos and lesson partially, but miss important elements along the way. I'll address each point below:

Before we move away from sausages, I do want to talk about how you go about employing the sausage method to construct your legs. The process laid out there is very specific, and while you may not find that the insect you're looking to draw matches the formula of a "chain" of sausages, what we're doing here is less about drawing the legs themselves, and more like creating an underlying armature or base construction. We can still later go on and add additional mass to those legs as shown here, but the key is to create a structure that maintains both the fluidity and gestural nature of the limbs, and still feels solid and three dimensional. We achieve the first part by keeping the width of the sausages consistent throughout its length (avoiding any pinching or swelling), and we achieve the second part both by keeping them simple and by being sure to draw a single contour line defining the intersection between those forms (or in other words, defining the relationship between them in 3D space).

The next issue I noticed is a tendency to trace back over your construction lines. Tracing is bad because it causes us to focus on how the lines exist on the page, in two dimensions, forgetting about how what we're actually drawing are edges that move through 3D space. Tracing tends to be done more slowly, adding wobbles and other complexity that undermine the illusion of solidity. Looking here on this image, we can see detail being added in two dimensions, on the page. Every mark you put down where you're thinking of your drawing as just a collection of lines will reinforce that lack of belief in the illusion you're trying to present to the viewer. As explained back in lesson 2, you have to continually remind yourself that you're arranging a bunch of solid, three dimensional forms together in a three dimensional world. That is ultimately what all these techniques and methodologies are working towards - to convince you. Once you believe it, truly, you won't have much trouble convincing the viewer. Of course, it's easy to believe something on a logical level, but it goes much deeper than that, and it is something we continue to develop and work at.

The last point I want to raise has to do with constructional drawing itself. Construction comes in two flavours:

Additive construction is where we place a solid, three dimensional form in the world, and then move forward by building further simple forms on top of it. As we build up these forms, each one existing as a solid mass in three dimensions, we gradually build up complexity. This is what we do most of the time, and it is what I recommend students do wherever possible.

Subtractive construction is the opposite - it involves taking forms that we've constructed in the world, and then cutting back into it. A lot of students immediately think, therefore, that what we see here on the back of this beetle is what we're talking about - but it isn't. What I'm referring to is where you drew your initial mass for the beetle's thorax, then decided that it did not fit the form you saw in your reference, so you drew another shape on top that cut back into the previous one. This is working purely in the 2D space of the page, and again - by doing so, you're reminding the viewer that you're just showing them a flat drawing.

In order to maintain the illusion that our drawings are in fact solid, three dimensional forms, we need to treat them that way from the beginning. This means that we see every single mark we draw as being part of a solid form that now exists within the world. That initial mass you drew existed in the world like a ball of marble. You can't simply have another form occupy the same space as something that is already present - you have to interact with it and actually deal with what is already there. This is where subtractive construction comes into play.

Subtractive construction is the act of taking a 3D form and separating it into two sections. We do this using contour lines, drawing along the surface of the form in three dimensions, as though our pen were a scalpel. Once this line properly divides the form into two sections, we can then designate one as being positive space (the piece we keep), and the other as being negative space (an empty void). Being that we still clearly define how both exist in 3D space, we still maintain the illusion, and are allowed now to cast aside the piece we don't want. You can see this demonstrated here in a demo I did for another student.

The thing is that additive construction is really good at helping the student further develop their grasp of how forms interact in 3D space, whereas it's very easy to slip back to thinking in 2D when working subtractively. As such, the more you work additively, the better your results will likely be when you have to work subtractively.

Now, all in all you're showing a lot of progress, but you're cutting a number of corners and taking shortcuts that undermine what you're trying to achieve here. As such, I'm going to give you a few more drawings by which to demonstrate your understanding of what I've explained here.