Another “Swamp” Plant

Swamp milkweed (Asclepias incarnata; Apocynaceae) is found in habitats similar to swamp candles (see previous post).  They’re pretty easy to distinguish from common milkweed (A. syriaca): the flowers are a richer, more saturated pink color, and are borne in flatter, sparser clusters; also the leaves of swamp milkweed are much more narrow.

I don’t have much of anything new to say about them (see this post from 2017); I just wanted to share a few pictures from early August.

Click on each picture to see it better.


Almost Done


A few asters, goldenrods, and eupatoriums are hanging on, but mostly the wildflower show in the Potomac Gorge is done for the year.  That means it’s time to watch for other interesting things, like autumn leaves, the shapes of bare tree branches silhouetted against the sky, foggy sunrises and clear sunsets.  And seeds.  Like these seedpods of common milkweed (Asclepias syriaca) that were just opening on the riverbank near Lock 8 in mid-October.



just opening, not puffed out yet








forming little balloons

















milkweed in early June20150610-20150610-_DSC0089

Monarchs (A Post for Cheryl)


Ta-da!  Here it is, the current darling of conservation, the monarch butterfly (Danaus plexippus).  I promised a friend I’d write about them if I ever actually saw one.  So here you go, Cheryl, this post is for you!

This one was in the Smithsonian butterfly garden on the National Mall, feeding on butterfly milkweed (Asclepias tuberosa).

The monarch is easily mistaken for another butterfly, the viceroy.  The two look a lot alike; the major difference is a dark lateral stripe toward the rear of the viceroy’s hindwings.  I don’t have a picture to illustrate that but have a look at the Maryland Butterflies website.

I’m no entomologist so I’ll stick with a few basic facts.

There are two populations of monarchs, one east of the Rocky Mountains and one to the west.

Most of the eastern population overwinters in Mexico, though some will hibernate on the Gulf and southern Atlantic coasts.  Adults already in the tropics do not migrate.

Monarchs lay eggs on milkweeds (Asclepias species, and two other species in the Apocynaceae).  The caterpillars go through five instars before pupating and emerging as an adult butterfly.  The adults will feed on a variety of plants, including species in the aster, carrot, pea, and mustard families.

Monarchs will produce one to six broods during the summer.  Most of the butterflies live only a few weeks; it’s the last brood of the year that migrates south to overwinter, mate, and return north, laying eggs on the way.

The eastern population has declined by more than 90% since 1995, which is about one billion individuals.

The major threat to monarchs is habitat loss, which takes two forms: destruction of the forests in which the monarchs overwinter, and destruction of milkweeds, the sole larval host plant.  Milkweeds are considered nuisance plants by farmers and many homeowners.  Another threat – and another reason to hate invasive species – is the increasing presence of two species of Cynanchum, exotic alien plants that look like the native Cynanchum laeve (which is a larval host plant) but are poisonous to the larvae.

Other species of butterflies migrate, but the monarch is the only one that migrates both ways.

For more detailed information check out any of the following sites:
USDA Forest Service
Butterflies and Moths of North America
Monarch Watch
The Xerces Society


Diptera or Hymenoptera? A Little Insect ID

Remember this picture from June 26?


bee on swamp milkweed (Asclepias incarnata)

A reader commented that it might not be a bumblebee – might not even be in the order Hymenoptera.  These things bug me, so I did a little research.

First, a quick summary of taxonomy: species of organisms are grouped into genera, which are grouped into families, which are grouped into orders, which are grouped into classes, which are grouped into phyla (for animals) or divisions (for plants), which are grouped into kingdoms, which are grouped into domains. (If you’re my age, you learned as a child that all life is in either the plant or animal kingdoms, a notion that was actually discarded before I was born, but I’m not going to sidetrack into the history of taxonomy; let’s just say that classification systems change as scientists learn more.)


bee on narrow-leaved mountain mint (Pycnanthemum tenuifolium)

There are 30 or so orders within the class Insecta (those wacky taxonomists are always redefining things, so it’s hard to say exactly how many).  One of these is Diptera, which comprises mosquitoes and flies.  Another is Hymenoptera, which comprises bees and wasps.

At this point, you night be wondering, isn’t the creature pictured obviously a bee? Not necessarily.  There are flies, like this one, and for that matter moths, like this one (yet another order, Lepidoptera), that look, superficially at least, a lot like bumblebees. has a page about bee mimics; it’s an interesting read.

The commenter on my blog pointed out that the insect in question appears to have only two wings, which suggests Diptera.  (That’s what “diptera” means: two wings.  Insects in the Hymenoptera have four wings.)


bee coming in for a landing on basil balm (Monarda clinopodia)

After more hours than I care to admit reading field guides and surfing the internet, I was still at a loss to say what this creature is, mostly because I couldn’t tell from the picture if it has two wings or four.  So I asked the expert: a friend who is an entomologist.  I emailed him the picture with the note “What order is this in? I’m not even going to say what my thinking is here”.  Here’s his reply:

“Hymenoptera. I know you are thinking Diptera, because it looks like it only has one pair of wings, but it actually has 2 pair. Hymenoptera have a series of “hooks” on the trailing edge of the front wing called hamuli, and these serve to link the wings together. You can actually see the two wings in this picture – the notch near the bottom of the “wing” is the demarcation of where the two wings join together. A give away in this photo that this is a bee and not a fly are the antennae, which are long and multi-segmented. Flies have shorter antennae, with fewer segments.”


a brief pause on the morning rounds

So, it’s a bee: class Insecta, order Hymenoptera, family Apidae, genus Bombus.


Bombus (probably) departing Monarda, en route to Erigeron

On the Asclepias Buffet

20150623-20150623-_DSC0134The milkweeds sure do attract visitors.  Pleased to discover a very small stand of swamp milkweed (Asclepias incarnata) in an easily accessible area, I decided to stay awhile to see who came by. Here are some of the insects I saw on it.


This is a pearl crescent butterfly, Phyciodes tharos, a member of the brushfoot family (Nymphalidae).  20150623-20150623-_DSC0105

See the blurry orange thing in the foreground?


That’s an assassin bug (species unknown, family Reduviidae). They sometimes hide in flowers, but more often actively hunt their prey*.  They use their rostrums to inject prey with salvia, which then liquefies the victim’s insides so that the bug can suck them out.

I have a sudden, strange urge to watch Starship Troopers again.

In less gruesome news, the milkweeds were also attracting the bees.


I have no way to identify the species of this bumblebee (family Bombidae).

[edited to add: see comments]

*Encyclopedia of Life