Thanks much to Mona, Dwayne, Monarch Mama, etc. I incorporated all your suggestions and the fatality rate among eggs and new cat hatchlings is almost zero! I bought shallow and 5-inch high plastic containers and had only 1 egg fatality (never hatched) out of the last 30 eggs collected. I put the collected eggs in a shallow plastic dish with a moist paper towel, then put the airtight sealer on. When the eggs start to darken, I transfer them into a separate airtight shallow container. Airtight = spider, assasin bug, ant- proof. When the dark eggs hatch, I place the new hatchlings into a third airtight, plastic container lined on the bottom with a moist paper towel. When hatchling reach 1st instar stage, I place them in a fourth container, a large aquarium with a screen top with cut milkweed stems placed in dog food cans protruding through holes cut in the platic can tops.
Today's tally shows 2 whitish eggs, 3 darker eggs ready to hatch, 6 cat hatchlings, 21 first instars, 10 larger cats in a large acquarium (ready to form J's), and 13 chrysalis'.
Thanks all! Robert at CREATE A WILDLIFE-FRIENDLY YARD