What is Egg Loading?
You’ve heard the statement, “Three’s a crowd!” Well, in the monarch world the same holds true. Laying eggs on healthy, lush milkweed plants is extraordinarily important. Emerging monarch caterpillars chew, munch and devour their own eggshell for nourishment, but they may also ingest the eggshell of another if close by.
For this reason the female seeks to lay her eggs very carefully – only one egg per plant. Notice the differences between the egg photos on this page! They tell a story.
When milkweed is scarce and a shortage affects the habitat, seeking out viable plants becomes difficult. The female reverts to laying more than one egg on the same leaf or plant. Also, if she is very tired near the end of her laying period, she may place three or more on the same leaf. “Egg loading” can occur when milkweed is not plentiful. Planting milkweed and nectar producing flowers to replenish deficiencies in the habitat is crucial to the future of the monarch butterfly… and the bees!
PHOTO: Holli Webb Hearn
Pretend you are a tiny little caterpillar! You are growing inside the tiny little white egg your monarch mother laid a few days ago on a delicious milkweed leaf. Your beautiful egg is not round, but oval in shape . . . like a football. Tiny lines can be seen on it from top to bottom. Eggs that are in the shape of circle are another type of insect.
Children playing in fields will be able to find you. If they look closely, they may even be able to see your tiny black head at the top of your eggshell. After three or four days, when the time is exactly right, you begin to chew a hole in the top of your eggshell. Your body has begun to grow and you are feeling very squeezed and cramped! There isn’t very much room left inside that eggshell. How exciting it is when you chew through the top of the shell.
Now you can peek out and see balloons of pink milkweed buds swaying in the warm summer breeze. If you look closely, you can see other eggs that another mother monarch has laid. She will lay hundreds of eggs in a day.
OK…now let’s get back to work. Keep chewing and when the opening is big enough, you can crawl out…push…tug…wiggle…squirm…squeeeeeeeeze your way out! WOW!
PHOTO: Edith Smith 2005
“Why should I do that,” you ask?
To protect hatching Monarch caterpillars and adult butterflies!
A hatching Monarch caterpillar eats its way out of its eggshell. If there are pathogens left by the adult butterfly as she laid the egg, the caterpillar eats the pathogens and becomes ill.
The Monarch Program website gives information about two common types of pathogens that attack Monarch Butterflies: Baculoviridae (nucleopolyhedroviruse) and Neogregarin (Ophryocystis elektroscirrha).
Baculoviruses are pathogens, like some human viruses, which attack insects and arthropods, while Neogregarin (Ophryocystis elektroscirrha) is a tissue specific parasite from the family Neogregarinidae. Neogregarin does not kill caterpillars, but adult Monarchs that are heavily infected often die before they mate, don’t live long, and are smaller than normal.
PHOTO: Holli Webb Hearn
It’s been an exciting morning, but now it’s time to do what YOU do best…monarch caterpillars are munching machines! They eat all day long! They munch, crunch, munch milkweed. Just look around…milkweed is growing everywhere! What an exciting view…off in the distance another little monarch caterpillar is busy munching milkweed, too. Now it’s YOUR turn to proudly start your day and say
“Hello world”…”I’m a monarch caterpillar!