Excerpts from Jim Conrad's
from the September 30, 2012 Newsletter issued from the valley of the Dry Frio River in northern Uvalde County, southwestern Texas, on the southern border of the Edwards Plateau, USA
A BLACK SWALLOWTAIL CATERPILLAR'S OSMETERIUM
My host gave me four large, healthy parsley plants, quipping that Black Swallowtail caterpillars really love to eat them. They'd defoliated the plants three times this year already, and now transplanted at the cabin for the fourth time they're losing their ferny leaves to about a dozen plump, zebra-striped Black Swallowtail caterpillars, one of which is shown above.
These are such handsome caterpillars, and the butterflies into which they metamorphose are so beloved and pretty, that we just let them have their way with the parsley. The parsley grows back; the butterflies' survival is more critical. And how could anyone kill a caterpillar with a face such as that shown below:
Swallowtail caterpillars are equipped with an orange, forked gland called the osmeterium which, normally hidden, emerges from the segment behind the head when the caterpillar feels endangered. The osmeterium releases a foul smell to repel predators. The chemicals exuded from the osmeterium varies from species to species.
The chemicals of our parsley-eating caterpillars smell somewhat of parsley. I know that because I just stepped outside, annoyed a Black Swallowtail caterpillar by tapping it on its side, causing his osmeterium to appear, and the caterpillar turned around and pressed the osmeterium onto my offending fingertip, which I then smelled of. You can see the upset caterpillar with orange osmeterium deployed below:
from the November 3, 2013 Newsletter issued from the Frio Canyon Nature Education Center in the valley of the Dry Frio River in northern Uvalde County, southwestern Texas, on the southern border of the Edwards Plateau, USA
This week a 5/8ths-inch long (15mm), second or third instar caterpillar turned up on my parsley, which you can see below:
Bea in Ontario assures us that this is indeed a Black Swallowtail caterpillar, despite it being so much smaller and different looking from the more developed, much larger, plumper and whiter one we photographed earlier, shown at the top of this page.