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Sunday, October 2, 2011

Milkweed World

Stop and look at a milkweed plant this week and you may see a lot of interesting and colorful insects.
Milkweed.


The monarch butterfly caterpillar, Danaus plexippus, is a milkweed specialist that eats nothing else.  

Monarch caterpillars come in five sizes. Each size is a different stage called an instar. Successive instars shed their skins and grow larger in abrupt steps. 
Check the area around milkweed plants carefully and you may find a monarch butterfly chrysalis like this. I saw a caterpillar curling up into a J shape in this spot under a fence rail yesterday. When I returned today it looked like this. A beautiful orange adult will emerge from the pearly green structure in about two weeks. 

Milkweed bugs, Oncopeltus fasciatus, suck milkweed sap; they have piercing, sucking mouthparts that are like sharp straws. These three milkweed bugs are warming up on a metal railing in a milkweed patch. The little guy is an immature stage called a nymph.
This milkweed tussock caterpillar, Euchaetes egle, will grow up to become a relatively unremarkable small brown moth. 
This is a yellow milkweed aphid, also called the oleander aphid. Aphids suck plant juices for nourishment. This adult is about a tenth of an inch long; you would have to line up a few dozen of them to make a line as long as their scientific name -- Aphis nerii boyer de Fonscoblombe.

Aphid populations grow quickly and can completely cover the stems and leaves of a plant. Tiny wasps help keep them in check. Wasps attack aphids by piercing and laying eggs inside them! The two brown aphids on the pod on the right of this photo are victims of wasp attacks; they are called mummies. Wasp larvae dine on the interiors of host aphids and eventually emerge as adults. 

Adult ladybugs like to eat aphids. (Look out little yellow guys!)
This is the ferocious larval stage of a ladybug sitting on a milkweed leaf. It eats aphids too. It came to the right place! 

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