Pete Dixon

I just had a last look at those two jars and this is what I came away with.

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The first jar's water probably had about 100 larvae total, the second had substantially more, in the order of 200-300. This estimate is based on how much water was in each jar and how much water I pipetted out of each into a petri dish and scanned. In the second jar that I launched 2 days after the first, I placed more stool onto the coffee filter. More stool = more eggs = more larvae. Collecting larvae from the first jar would have been more work as the larval density in the water would be less and more time would be required to find them. To put this into context, from the first jar several mls of water sometimes wouldn't have any larvae at all. In contrast, from the second jar several times I had 5 larvae in the microscope's field of view at once (@ 40X that's only 5mm, or a small drop). The latter makes for easy work.

So from the two jars my yield was 300–400 larvae. On my current program, I only need 10 larvae every two months. In other words, an ample supply 

I did try the trick of placing jar water in a wine glass in the hope that the larvae would settle to the bottom, but I really didn't see much of a difference.  

Going forward, I'll keep doing two jars and increase the stool on the filter. I'll reinforce the thread supporting the filter to ensure the extra weight doesn't collapse the filter into the water. Maturation of the eggs into larvae is heavily influenced by temperature (90°F means 5 days, 68°F would take 9-10 days). I'll be taking that into account for the next incubation.

Scuttlebutt on the HT Discord server is that sometimes incubations fail for no obvious reason. Perhaps the hookworms in the gut take a rest and don't produce eggs, or perhaps they get stunned by antibiotics taken by the host, or by food that was eaten the hookworms were sensitive to. For that reason, I think it makes sense to have two jars going at once as insurance, preferably launched several days apart.

Incubation has turned out to be both simpler and easier than I expected. There's really very little effort once you get the hang of it, and the cost saving is substantial.