While raising caterpillars I have learned a lot about the importance of predators. Without them we would have millions of diseased butterflies flying around. In nature only the fastest and healthiest caterpillars make it to adults. I think only 2 or 3% of butterfly eggs laid survive to adulthood.
I have had Monarch butterflies lay hundreds of eggs in my garden, but have not found one caterpillar make it to a butterfly. With so many wasps attracted to my milkweeds they quickly spot the caterpillars for lunch. I’ve found small monarch hiding in my parsley and other bushy plants, but somehow the wasps manage to find them.
This lizard stays around my garden in wait of a tasty caterpillar.
The best solution for avoiding these predators is to keep the caterpillars protected in an enclosure. If you want to purchase a smaller size cage to raise caterpillars the best place is http://www.butterfliesetc.com/buy-butterfly-caterpillars/caterpillar-rearing-containers. Small netted containers sell for as low as $10 dollars. I have had great success with using enclosures. Out of 70 eggs about 60 emerged as healthy butterflies. Around ten percent died from a disease called OE.
Ophryocystis elektroscirrha (OE) is a small parasite that infects only monarch and queen butterflies. A female butterfly with OE can transfer an OE spore to its eggs. When the egg has an OE spore on it, it will ingest it when eating the egg shell. The only way to destroy the parasite is to clean the eggs with a bleach solution. To learn more about OE and how to clean eggs go to http://www.butterflyfunfacts.com/oe.php.
Right now I am trying to learn more about OE. I selected four of my monarchs that appeared to be OE free. I kept them in my pavilion ( with nectar and fruit to drink ) until they laid eggs on my milkweeds. Now that the eggs have hatched I am watching the caterpillars to see if they get OE or if they all stay healthy. If the caterpillars have OE they will start to develop dirt like spots on their bodies when older.