As polar didn't give adittional steps, I'll add to his critique:

Starting with the organic forms with contour curves, you're doing a pretty good job with them. Both the shapes and the curves are confident and neat. The main thing with them is that their points are a little bit too pointy. Keep in mind that the ends should be formed by a ball, so the ends should be affected by it.

There are also some places where your ellipses shift a little bit too quick which results on making the sausages look a bit flat, so watch out for that too.

Now onto the insect drawings. You're overall making a pretty good job on those, they're solid, but there are a few things I want to comment on that are very important, both on this lesson and on lesson 5, so I want to make them clear.

-Intersections between forms are part from the constructional drawing, and not detail. I want to make sure you know this so you don't skip it on the next constructional drawing that you do. Detail is basically textures as described in lesson 2, so other than that it's all part of construction.

About the intersections between forms as well, you sometimes skip them. Some examples are the connections between the body parts of the louse, the scorpion head and body connection, the fly, bees etc. One example where this is approached well is on your first beetle connection between the body and the horn (even though you're skipping constructional steps on the horn, which I'll comment later).

-Second thing I want to point out is to try to pay more attention on the demos, don't just follow them blindly. There are some demos that are outdated for example, and being critical is specially important on those. The example I'm talking about is the scorpion demo. On this demo, uncomfortable misjudges the size of the box of the scorpion and has to make a cut to make it fit, and you do it as well. Try to be more careful with those things. And about the outdated material, text will always be more important than the videos, so if there's something written on the text that is contradicted in a video, follow the text.

-Third thing is that you have a tendency to ignore your underlying construction at times.

Basically, when you put down a form on the page, it's there. You can't ignore it. It's a real 3d mass and you need to accept that. So build into it, don't treat it as if it's a 2d guideline. Here are a few examples where you do this, hopefuly it makes it a bit more clear: First, and second

-Fourth thing is that you sometimes add forms with flat shapes instead of actual forms. When you add a form to a drawing, draw first that form, and then the connection to the other forms on the drawing with an intersection.

First example is on the wasp, you add the forms with a simple shape instead of a form. When drawing bulking sausages you should approach them like this

Another is on the beetle here

-Next is pretty similar, and it's skipping constructional steps. There are some places where you're going too complex too fast when you could have broken those down in more steps. Some examples:

First, Second, This one is simpler, similar to how leaves should be approached in lesson 3, and Third

-Another thing is that you tend to overuse contour lines. Doing just the intersections between forms is enough if you do them well, so focus on those.

-I want to comment as well that you're drawing too small. Probably because you wanted to fit more drawings into the page. I would have liked to have seen some very big drawings, and I do think that drawing this small has hindered you a bit.

-And lastly, even though most of your lines are pretty confident, in some of them, specially on contour curves, you hesitate and make them wobbly. Don't forget to apply the ghosting method always, even to contour curves.

Like I said, you're doing a pretty good job, drawings are very solid and clean, but I want to make sure you understand some of the concepts of this lesson, so I want you to do 1 more drawing, give a shot at this crab

Good luck and keep up the good work!