Skipping Sachems

It's mid-afternoon, sunny, warm and breezy and numerous Sachems (Atalopedes campestris) are migrating through, counting about 25 in the last 45 minutes. They dart from flower to flower, sometimes with 2 or 3 fighting for a flower and then zooming off to the other side of the garden and then back again.

They are part of the great family, Skippers, and are in a small Genus, Polites Scudder of just 10 species, all in North America, 6 occurring in the East and only 2 with ranges that extend beyond the US. Most of them are small, orange and black and have short antennae.

The dark wings and transparent square spots at the end help identify 

this beautiful female Sachem. 

Set against a colorful backdrop of zinnias, a Sachem Skipper inserts 

its proboscis quickly into the flower 

  down deep, obtaining nectar for it's long flight,

 and then back out again.

 The large black dot on the forewing of this handsome skipper identifies the male Sachem. 

Only a little over an inch long, this little guy, froze and then 

slowly stuck his proboscis at me.

The chevon on the outer upper wing, also is commonly seen in Sachem Skippers. 

They are headed down South, passing over southern US, through Mexico and mainland tropical America to Brazil, where they will overwinter.

For further information: https://www.butterfliesandmoths.org/species/Atalopedes-campestris

Peterson Field Guide, Eastern Butterflies, 1998.

Swallowtail Butterfly Mimicry

While I was out to the garden, collecting a sprig or two of parsley for a veggie stir fry, I was startled by a beautiful caterpillar:

When I looked closer, there were over 10 of them in my parsley patch.

After some investigation, I identified them as the Eastern Black Swallowtail Butterfly (Papilio polyxenes) caterpillar.

They start as a little greenish-yellow iridescent egg, from which emerges after 4 to 9 days, depending on the weather, a black larvae, with a conspicuous white saddle, which mimics bird droppings. This stage lasts 10 to 30 days, and includes several instar phases and a caterpillar.

https://s-media-cache-ak0.pinimg.com/736x/7d/bc/10/7dbc104ea2a0febc2535a05f54c1c452.jpg

Another 9 to 18 days, as a pupa, are needed to become a butterfly.

Black swallowtail butterflies frequent the zinnia garden, 

but wait, after some double checking, I find these butterflies are NOT Eastern Black Swallowtails, but a dark morph of the female Eastern Tiger Swallowtail (Paplio glaucus) and their caterpillar looks like this:

https://en.wikipedia.org/wiki/Papilio_glaucus

Female Eastern Tiger Swallowtails are dimorphic and this chart from Wikipedia shows the differences :

3 - dorsal female dark morph; 6 - ventral female dark morph

"In the dark morph, the areas that are normally yellow are replaced with dark gray or black. A shadow of the "tiger stripes" can be seen on the underside of the some of the dark females."

From one of the photos above, I zoomed in closer, and indeed, you can see the "tiger stripes":

So the differences are easier to identify, pictured below together are the female Eastern Black Swallowtail and then the female Eastern Tiger Swallow tail- dark morph.

Note the prominent white spots on the body and wings, for starters.

https://en.wikipedia.org/wiki/Papilio_polyxenes

Eastern Black Swallowtail (Papilio polyxenes)

Eastern Tiger Swallowtail - dark morph (Papilio glaucus)

There is also a Spicebush Swallowtail (Papilio troilus), which also looks similar:

https://en.wikipedia.org/wiki/Papilio_troilus

and all these dark swallowtails are mimicking the poisonous Pipevine Swallowtail (Battus philenor)

This is called Batesian mimicry, where the butterfly's resemblance to a noxious one, protects it from predators.

There are numerous interesting scientific articles on the subject, but these two studies are especially relevant. In Evolution (33 (1) March 1979), "Batesian Mimicry: Field Demonstration of the Survival Value of Pipevine Swallowtail and Monarch Color Patterns" by M.R. Jeffords, it was shown that mimetic swallowtail butterflies have longer survival times, and are less frequently and vigorously attacked by predators.

Also, why are only the females mimetic? 

In an article in Trends in Ecology and Evolution, titled "Diversity in mimicry: paradox or paradigm", by M. Juron, three possibliities are offered, including 1. being mimetic reduces mating success in males, 2. reduces success competing against other males and 3. since females are more vulnerable to predators because of their predictable behavior while feeding, mimicry would offset this. 

Here is a link to the full article: 

https://www.researchgate.net/profile/James_Mallet/publication/222493255_Diversity_in_mimicry_Paradox_or_paradigm_Trends_Ecol/links/0046351957a31efe09000000.pdf

A simple visit and observation in the garden led to just a peek 

into such a fascinating and 

complex world.