Friday, September 9, 2016

Munch a Bunch!

When you're a Monarch Butterfly caterpillar you cannot afford to be wasteful.  You have 10 - 14 days to grow from a tiny spec of an egg and become a chrysalis or pupa. Nutrients are a valuable resource not to be wasted and discarded.
The first meal a newly hatched monarch caterpillar eats is it's egg case. The minerals and nutrients in this egg shell is the first step to becoming an healthy larva.
After eating the egg case the 1st instar caterpillar begins to eat the hairs on the milkweed leaf which also held it's egg. After the hairs the caterpillar will start to eat the leaf proper. This young caterpillar is not big enough yet to chew entirely through the leaf but within 24 hours of hatching that will be possible. In the next two weeks the caterpillar will eat the equivalent of 6-8 large  common milkweed leaves.
As the caterpillar grows to become a chrysalis it will need to shed it's skin 4 times as it's body outgrows that skin. This caterpillar has just shed it's skin and will rest for about 90 minutes afterwards. As it rests it's head, feet and pro-legs will get the distinctive black and yellow coloration that is absent immediately following the molt. Notice the anterior tentacles are still folded back against it's body. These will slowly extend forward over the next two hours.
As with the egg case, the caterpillar turns and proceeds to eat it's recently shed skin to retrieve the nutrients in that skin. This will take place after each molt. The only thing not consumed is the molted head cap seen laying behind the caterpillar.
Photos by: Jeff Ormiston

Friday, September 2, 2016

Spicebush Butterflies

While the numbers of Monarch Butterflies seen in Northeast Indiana has been very disappointing this summer of 2016, the numbers of other butterflies have filled the void of the missing Monarchs. Most prominent among these have been the swallowtail butterflies. Giant Swallowtail, Eastern Tiger Swallowtail, Black Swallowtail and Spicebush Swallowtail have been seen in large numbers to the delight of midwestern butterfly afficionados.
Spicebush Swallowtail, Popilio troilus troilus, early instars form a shelter by laying a web mat near the edge of the host leaf. As the web drys it contracts and folds the leaf forming a shelter for the growing caterpillar. The caterpillar hides in the shelter during the day and comes out to feed at night thus avoiding the possibility of being eaten by the common caterpillar predators. Host plants for the Spicebush Butterfly is Spicebush, Sassafras and Tuliptree among others.
As an early instar the main means of protection is looking like a bird dropping.  The brown 3rd instar caterpillar, with the white markings, makes a very convincing specimen. The green 5th instar caterpillar uses its false eye spots and humped body segments to look like a green snake and discourages predators. Notice that the black eye spots are complete with false reflective eye highlights.
The actual head of the caterpillar is usually tucked under the anterior of the body for protection.
To further promote the charade the caterpillar has a forked osmeterium that, when fully extended, resembles the forked tongue of a snake. The osmeterium also is coated with sticky, foul smelling slime that discourages those that would make the caterpillar lunch
 As the caterpillar gets closer to forming a chrysalis it begins to change color to a shade of light yellow. Finally it climbs a convenient stem, attaches a string seat belt and waits for the pupating process to begin
Chrysalises that form during periods of short day light (autumn) will be brown in color to blend better with the browning leaves of fall.  Chrysalises which form during periods of long daylight hours (summer) will be green to blend better with the green leaves of summer and emerge as adults that will lay eggs before cold weather sets in.  Chrysalises that form in late summer and early fall will enter a state of diapause, or suspended development, and emerge as an adult as the warm winds begin the following spring. 
Adult Spicebush Butterfly (male) 
Photography by Jeff Ormiston