I'll start out by answering your questions:

1. The references can be useful, but only in certain circumstances where I really can't make out why you might have done something a certain way, or if I want to demonstrate how I'd tackle a particular problem. In most cases I don't end up using them, so you don't have to include them if it's a pain. Most don't.

2. Correct. Looks like I used the word "circles" in the louse demo, but should have really said ellipses.

3. You can draw them in separate segments. When it comes to more complex forms, breaking them up is okay as long as you don't leave gaps, and make sure that in the end they feel like one cohesive piece.

So looking over your insect constructions, there's some definite strengths and significant progress, as well as a number of issues I'm going to address. As this is critique 14 of 23 today, I'll jump right to it.

We're going to focus a good bit of this critique on the dragonfly at the bottom of this page. I love this dragonfly - not because it's drawn especially well, but because it exhibits a common mistake that is a lot more subtle in other drawings, and that makes it way easier for me to address.

Looking at the abdomen, we can see how your first move was to block it in with a simple ellipse/ball form. Now admittedly in this particular case some kind of a sausage form would have been much better, but that's not really why I'm focusing on it. Rather, it's that you noticed the fact that a different kind of form would have been better, and so in the space this ball form was occupying (being that it's a three dimensional form existing in the world now), you placed another entirely different form. This gives the viewer something of a contradiction - two possible, but mutually exclusive ways in which to interpret the drawing. Either there's a larger, stretched sphere there, or there's a narrower sausage there, in the same place.

These kinds of contradictions are problematic because they basically tell the viewer that something is wrong, and that what they're looking at is not possible. You can't have two separate ways of interpreting something, there has to be one clear answer. As more of these contradictions build up in your drawing, they'll undermine the suspension of disbelief in the viewer - but this abdomen issue is a big one, and it on its own is likely to make it clear to most viewers that they're looking at a flat drawing.

So, what can we do? We've drawn a long ellipse/sphere form and it is different from our reference image. The sad truth of it is that in order for construction to work, you need to constantly be building on top of each phase of construction - not ignoring things you've already drawn, but working with them. In most organic constructions, your only real option is to say, "well this dragonfly's gonna have a real chubby abdomen" and wrap your segmentation around the form you'd drawn. In more hard-surface kinds of drawings, subtractive construction becomes an option.

Usually when students make the mistake of basically trying to ignore something they've already drawn, they think they're working subtractively (I put down a form, now I'm going to cut across it to create the form I really meant to make), but what they're actually doing is cutting across the two dimensional silhouette of that form. Interacting with a form in two dimensions is just going to remind the viewer that they're looking at a two dimensional drawing, and so that's not really an option for us.

Now, this was by far the most obvious case of this kind of mistake, but we can see others. This ant's thorax was initially blocked in with a much larger ball than the form you dropped in after it, and to an extent so was the abdomen. This caterpillar was first blocked in with something sausage-like, but then when you actually built the bulging sections of its body, you cut back into that initial form's silhouette.

There may be situations where you draw an ellipse and it comes out somewhat loose, with lines in a few different places, (since we purposely draw through our ellipses 2 full times before lifting the pen). Ideally we want our ellipses to be tight despite doing this, but if they don't, you might wonder where the "real" ellipse actually is. In these cases, treat the outermost perimeter of the shape as being the true extent of the form's silhouette. That way you won't end up with any of its lines spilling outside of what you treat as solid, 3D forms.

Now, if we ignore the issue I've been addressing this whole time, there are a couple other smaller ones but all in all you're doing a pretty decent job. For example, if we look at this page, you're showing an attention to detail that's coming along well, and your approach to the segmentation of their bodies is coming along well. The amin issue that I'm noticing is that you're not consistently applying the sausage method to constructing your legs in a consistent manner

Now it's totally normal to think that the legs of your insects don't look like chains of sausages, so you might think to modify how it's applied. Don't. The sausage method has a very specific goal and purpose, and should be used for every leg you draw, even into the next lesson's animal drawings.

The sausage method is focused not on drawing the entire leg, but rather on creating an underlying armature/structure that appears both solid and gestural. Most approaches for drawing legs will tend more towards one or the other, appearing solid but stiff, or gestural yet flat. The sausage method, when done precisely as outlined in that diagram, accomplishes both in equal measure.

Once in place, we can then wrap additional masses around its structure to add bulk wherever it's needed, as shown here, and even in this example involving a dog's leg. So, make sure you're applying the sausage method when constructing all of your legs - and not just in half measures. Make sure each sausage is a "simple sausage form" (two equally sized spheres connected by a tube of consistent width), that they overlap a decent amount, and that the joint between them is reinforced with a single contour line.

Overall I think your insect constructions are coming along well, but these key issues are holding you back a lot - to the point that I think you can draw these vastly better, based on what I'm seeing from you now. The key is to approach construction in a more structured fashion, to understand that every single mark you draw is the addition of a new three dimensional form in the world, and that with each one, you're building upon the existing solid structure. Right now you're close to grasping this, but are still willing to make a lot of shortcuts that involve treating things as flat drawings, rather than really believing in the illusion you're creating.

So, I'm going to assign a few additional pages for you to do in order to demonstrate that you understand these concepts. You'll find them below.