Wednesday, July 27, 2011

Bike Biology: Black Swallowtail Butterfly

What cyclist hasn’t been awed by the fanciful flight of the swallowtail butterfly as it flits over field and flower? Can a bicycle route exist that excludes its presence? In truth, only if it’s in Antarctica.

The swallowtails are some of the largest, if not the most often observed butterflies this time of year.

Swallowtail butterflies get their name because of their wing extensions that resemble the forked tail of some swallows. For Tar Heel cyclists, there is a historical connection with the butterfly to our state, according to one authority:

The tiger swallowtail is probably our most recognizable swallowtail in the eastern United States. It is admired by butterfly gardeners and treasured by young butterfly collectors. The first drawing of a North American swallowtail was of a male tiger swallowtail and was drawn in 1587 by John White who was commander of Sir Walter Raleigh's third expedition to North American.

The reader will immediately recognize the following lithe lepidopteron, a tiger swallowtail, from its picture.
This communication, however, is not about the tiger swallowtail, but its related cousin, the black swallowtail. Not because the tiger swallowtail is insignificant, but because of the presence of black swallowtail caterpillars, the cute critters in the lead-in photo, munching on fennel in my garden.

Initially, I erroneously thought that the caterpillars were those of the monarch butterfly. But, as one of my riding companion, Janis, objected, “Monarch caterpillars eat milkweed.” Something I knew, but rationalized that monarchs might like southern cooking, given the opportunity.

What changed my mind? Why did I abandon monarch in favor of swallowtail for the caterpillars lined up at the all-you-can-eat salad bar in my back yard?

The bottom line: anatomy. In this case, the presence of a certain anatomical structure—an osmeterium—common only to the family Papilionidae to which swallowtails belong.

Swallowtails differ from all other butterflies in a number of anatomical traits. Most notably, their caterpillars possess a unique organ behind their heads, called the osmeterium. Normally hidden, this forked structure can be everted when the caterpillar is threatened, or forced out with a gentle squeeze, and emits smelly secretions containing terpenes.

Check out the orange structure at the head end of the poor aggravated fellow, below, that reveals his true colors (lineage). Is he flashing an osmeterium or a peace sign? I was able to get "my" caterpillars feasting on fennel to flash me when I provoked them, touching them gently just behind the head, their orange osmeterium visible for a couple of seconds before being retracted.

Lastly, one can distinguish female and male black swallowtails, something biologists refer to as sexual dimorphism.

A male of this species has a yellow band near edge of wings; a female has row of yellow spots. The hindwing of the female has an iridescent band.



Let’s ride!


skiffrun said...

So ... I started reading this post, wondering what insights or where Mike was going to take this story that began with butterflies. However, when I got to one particular word -- lepidopteron -- I knew the aurthor was not Mike, but instead was Dean, and also knew that the article was going to be more factual science lesson than anything else -- although possibly a phun science lesson.

Luckily, author Dean has been chastised by Janis for more than just being confused about what it is that Monarch butterflies eat. She has also chastised / begged / demanded-of him to PLEASE occassionally use the common names for things. I find that particularly useful as I do not speak or read Latin or Greek (or Russian).


dean furbish said...

Thanks, skiffrun. I've tweaked the title to provide better context.

I saw some female butterflies this mornining checking out the salad bar and staus of recent progeny?

skiffrun said...

Dean, I wasn't making a criticism or critique -- just an observation -- perhaps indicating that one can discern style (or something) differences between you and Mike (even without "bad puns and worse jokes").

The future trick might be to see if I can discern your authorship before appearance of bad puns, worse jokes, or too much Latin.

(Please keep up the bad puns, worse jokes, and even the Latin and the Greek interspersed in the science and phun physiology lessons.)

By the way, it is still true what I told you when I first met you: "I enjoy your phun physiology posts even though I usually understand less than half of what you've written.