You can purchase my Fly Lab here

Or, you can just provide the following materials and have students draw and observe.

Each pair of students will need a dissecting microscope.

If you do not have that many microscopes available, most of the lab can be done with magnifiers.

I even have students take photos with their phones and zoom in to magnify.

I collect dead adult flies throughout the year.

I find them in windowsills, at work (who even knows why all those dead flies are in a storeroom.....), sometimes outdoors.  Sometimes I end up with a lot of adult flies after my maggots emerge from their pupae after lab.

I store dead insects in mint tins.  I got all of the empty mint tins I needed by sending out a donation request to my whole district.  Staff have been saving and collecting their mint tins for years. 

Wash the tins thoroughly with soap, then line them with a tissue to protect the dead insect.  Dead, dried insects are very fragile.

Remind the students not to pick up the dead flies - their wings will break off.  If they need to move them, they can use tweezers or forceps.  BUT - the benefit of using mint tins is that they are the perfect size to just place right under the dissecting microscope!  So students probably will not even need to move the flies around to see them well.

I buy maggots at bait shops.

The past two years, it's been much harder to find maggots as bait in my town.  This year I bought soldier fly larvae (used as reptile food) at a local pet store.  They look a little different than blowfly larvae, but are similar enough to work for lab.

I do not usually have students use the maggots that hatch from the fly eggs I collect, because I don't want the students touching the decomposing meat.  I worry about bacterial contamination.  

I do have students observe maggots that have just hatched and are still in the egg/meat container, but I do not let them remove the maggots from the container.  I have them put the whole container under the microscope.

Maggots need to be stored in the fridge to slow their development.

You'll need to use them within a few days of purchase.

When using your maggots, don't get them all out of the fridge at once.  I give a maggot to each lab group in a clean petri dish (so they can see it crawl around), and keep the rest of the maggots in the fridge so they don't pupate.

Don't let kids leave the maggot on the dissecting microscope too long or the light cooks them, and then that's just sad for everyone.

The maggots that I buy for lab eventually pupate. 

I save those pupae in mint tins, the same way I store dead adult flies.

The only way to get fly eggs is to convince flies to lay the eggs on meat.

I use mostly raw liver for this.  I've also used outdated ground beef I found in my fridge.  Liver seems to be the preferred food source.  I've tried both beef and chicken liver, and both seem to work.

I tried other food sources, like cat foot - the flies were not interested.  Liver seems to be the most stinky and appealing to flies.  Liver is soft, so the maggots are able to eat it.