Marvelous milkweeds

I am a huge fan of milkweeds due to their special attraction not only to monarch butterflies but also to a considerable list of other insects that are milkweed specialists, and some generalists who use milkweeds as a community to forage in. But the problem is that those of us that own hay fields will cut the grass including the milkweeds once or usually more per year, slaughtering the marvelous milkweeds. However I have come up with a compromise that I think both feeds the cows, and preserves the milkweed community. See what you think of my solution.

My plan is to cut the grasslands only once per year and that is in mid to late June in our location here in the SW Virginia mountains. This serves not only to harvest the grass for use in fodder but removes woody vegetation that invades the grasslands, and removes a layer of cold-season grasses (such as fescue) that are primarily exotic to this area. This releases the warm-season grasses and allows them to grow and produce a crop of seeds by Fall for use by native birds. But you may ask what about the milkweeds and their fate? It appears to me that this regime may actually be beneficial to the milkweed community in the following way. I retain a certain number of fields that are not cut except very occasionally (they are burned every three years in late Winter) and which have natural populations of milkweeds (in this case mainly the common milkweed, Asclepias syriaca). The fields that were cut this year on June 17 began about seven weeks later in early August to produce a wonderful crop of milkweed flowers, while the uncut milkweeds are setting seed and are no longer blooming. The leaves of the uncut milkweeds are old and tough whereas the cut and regrown milkweeds have young tender leaves. Thus my single-cut method of harvesting hay fields stretches out the milkweed season but does not obliterate it, as would happen if the fields were to be harvested a second time, a common practice among farmers to maximize hay production. Also I have noticed that the monarchs often do not arrive in this area in time to fully utilize the naturally cycling milkweeds, and indeed seem to use the "second crop" milkweeds extensively.

Some illustrations of the re-grown milkweeds are shown in photos of an adult monarch gathering nectar from a "second crop" flower, of a female yellow morph tiger swallowtail also nectaring on a re-grown plant, and a monarch caterpillar feeding on a re-grown leaf. Surely there is much yet to learn about the characteristics of milkweeds that are cut and then sprout again- do they provide proper food at tolerable levels of toxins, and in a timetable that is appropriate? Certainly it appears from my observations that this is a win-win situation that can preserve the habitat of many species that depend on milkweeds while also providing some income for the farmer. Of course subsequent hay cuttings must be sacrificed for the pleasure of observing and fostering the milkweed animal community, and providing enhanced food and cover for birds in Fall and Winter.

One of the other lesser known insects that I encounter among our milkweeds is a bit sinister- the famous assassin or wheel bug (see photo)! It is a predator with a wicked beak, a poisonous bite and a reputation for delivering a painful zap with its tubular mouth. It eats insects that come to the milkweeds and it would be interesting to observe whether it is capable of devouring those that are protected by the milkweed toxins, in contrast to others such as tiger swallowtails that are not.

So many puzzles and so little time! So get out there and check out the milkweeds and their fascinating inhabitants.

Bill Dunson

Galax, VA

Englewood, FL

The Io moth & caterpillar- some amazing natural designs

On a nature walk this morning at Stump Pass State Park in Englewood, FL, our group came across two caterpillars of the Io moth (see photo). At this stage they are a striking light green, with a red and white stripe along their sides. The younger caterpillars are brown to orange-brown. Although we were tempted to pick this beautiful green caterpillar up, I knew that this species has poisonous spines that can cause a lot of pain. One might assume that the green coloration is for camouflage, although it is so bright that it might even be considered a warning coloration along with the red/white stripes. The branched, poison-bearing spines pack a powerful jolt to any potential predator.

Strangely enough it was about three years ago that I saw the adult of this strange moth at our farm in Galax, VA. The unusually colored adult moth appeared on a window screen one morning where it must have been drawn to the lights the night before (see photos). With the wings closed the moth is cryptic in the right background and would presumably escape detection by most predatory birds. If it is detected and is poked, it opens its wings and reveals a marvelous set of false eye spots (see photo). Many moths have eye spots on their hind-wings that mimic an owl's face or just provide something scary for a bird to think about. But the Io moth has what I consider the most impressive set of eye spots. But even so I am amused that a bird would find this intimidating.
One again we can be amazed by the evolutionary process that can lead to the development of such a remarkable pattern. The variety of animal coloration is a never ending source of wonder.
Bill Dunson
Englewood, FL & Galax, VA

A tiny legume destroyer- the Genista moth

Another one of those things that go on in our backyards without much notice is the occasional destruction of plant leaves by small caterpillars. Sometimes we get annoyed by this and spray the plants or try to figure out what is happening. In recent walks in scrub habitat at Lemon Bay Preserve I have noticed that many of the beautiful sky blue lupines, which are not yet in bloom, are being heavily damaged by a small caterpillar (see photo attached). I was unfamiliar with this species and searched the web to find out that it is well known as a destroyer of various legumes, including lupine and members of the genus Sophora which includes necklace pod in Florida.
The rest of the story is that this caterpillar is immune to the powerful toxins found in legumes, and indeed uses these poisons to defend itself against attacks by predators. If this reminds you of some other famous cases think about monarchs and milkweeds, and zebra butterflies and passion-vines. So here is another case of a larval insect stage making itself toxic by eating a poisonous plant. Consider what this means- that the ability to tolerate the toxins must have evolved over a very long period, and then coloration advertising the toxicity (aposematic or warning coloration) developed. Then predators must recognize the significance of the warning coloration, perhaps specifically or generically. Some predators such as lynx spiders apparently can handle the toxins and eat the caterpillars (see this article). Now the adult is distinctively colored (see photo from web) but I do not know if it is protected also.

So if we needed reminding that the natural world is amazingly complex and interesting, here is another case. The deeper we look the more we see, and the more impressive the web of life becomes. So get out there and groove on nature but don't eat the caterpillars!

-Bill Dunson, Englewood, FL

Some Late Summer Photography