I have a number of things to point out, but I found it easiest to have first marked it out in this image, and to address each point below.

1. As discussed back in Lesson 2, you should absolutely not be dividing your drawing up into an "underdrawing" or "sketch" (basically marks you don't feel are part of the final drawing, and therefore purposely draw more lightly or faintly with the intent of hiding them, and a "clean-up pass" (marks that are much heavier, usually drawn with more hesitation. Constructional drawing is about every single form you draw being a solid, 3D entity within the scene, and those forms connecting and relating to one another in clearly defined ways, and this kind of approach contradicts the spirit of construction. Instead, you need to treat every mark you put down on the page as being solid and three dimensional (as I believe I mentioned in my original critique). If you're going to put down a simple ball form to represent the abdomen, then you need to go on to wrap other forms around it for segmentation - not just ignoring it in a way where the original mass could just as well be erased from the final result. Each entity is a part of the final construction, and each and every mark should be drawn with confidence. If you look at any of my demonstrations, you'll see that I don't take any steps to hide things, and so neither should you.

2. The shell on that beetle in your first drawing reads entirely as a flat, two dimensional shape, rather than a solid 3D form entirely because of how it lacks any clear relationship with the underlying, simpler structure of the abdomen (the one drawn in with a faint line). The initial mass doesn't feel that solid on its own, since you didn't really go to any effort to make it so (doing the whole underdrawing thing), but since it's a much simpler shape it's easier to interpret it as something three dimensional. Construction works under the premise that we can build upon a simpler scaffolding, and as long as we define the relationships between our newer, more complex forms, and that existing 3D structure, then we can make the new addition feel 3D as well. What you did here was largely taking a complex shape and stamping it on top, without defining any actual relationship between it and the form beneath. No attempt to wrap it around that structure, and so it just sits on top as part of the flat drawing.

3. There are a number of important elements of the sausage method that you're skipping over. While as you move through the drawings your sausages get better at sticking to the 'simple sausage' characteristics, you pretty much always skip the important contour line that should be used to reinforce the joint between sausages as shown here.

4. Similarly to what I explained in my previous critique about not cutting back across the silhouette of a form (because this will immediately flatten out your drawing), manipulating the silhouette of a form in any way is generally considered to be damaging to the illusion we're trying to create. If you want to add bulk to a sausage form, do so by adding another form that wraps around it, as shown here. The key is establishing a relationship between the original form and the new one.

Now, while I'm largely disappointed in the first three drawings, the last one is vastly better, and shows a total shift in how you're thinking about constructing in 3D space. I'm not entirely sure what changed, but it gives me a lot of hope about your understanding of the concepts, even if you weren't doing the best job with them initially.

Now, one drawing alone isn't enough to pass, and there are still aspects of the issues I lived above that are still present even here, even if to a lesser degree. So I'm going to ask for another 4 drawings, with the same restrictions as before.