Monday, August 3, 2020

Life in the Milkweed patch

By Beth Sullivan

Anyone who has spent time in fields , meadows, or wetlands is very likely to be familiar with at least one species of milkweed (Asclepias). Some of us, who spend a lot of time in those habitats are pretty familiar with several kinds of milkweed and many of the creatures that associate with it. A patch of common milkweed (Asclepias syriaca) is quite robust and can form large colonies as its roots spread and stems multiply. Swamp milkweed (A. incarnata) is a bit more delicate, a uniform pink with slightly fuzzy leaves. As its name suggests, it prefers wetter soils. Butterfly weed (A. tuberosa) is a shorter bushier plant with bright orange flowers and favors sunny, drier sites. As a species, milkweed is known for its milky sap which is actually toxic to most things. We would not die, but would likely be quite sick if we ate a salad of milkweed sprouts or leaves, as the sap contains chemical compounds which can be fatal to smaller creatures. Most children know the story of how the monarch butterfly is poisonous to birds, and that this protection comes from the milkweed plant. The adult butterfly gathers nectar from many plants, but lays its eggs only on milkweed. When the eggs hatch, the larvae begin to feed on the leaves and ingest the toxins. This does not hurt them, but actually makes them toxic in turn. Very few birds will attempt to eat the fat, juicy monarch caterpillars, and when they emerge from their chrysalis, the adult butterfly is toxic as well. The bright orange and black markings are known to be warning signals to birds or other predators that there is a danger present. Other insects also display black and orange colorations and in turn are protected by mimicking the monarch.
A monarch will take nectar from many flowers but the swamp milkweed is favored for laying her eggs.

Beautiful common milkweed

Only one egg is deposited under a leaf, ensuring the monarch caterpillar an immediate food source.

 Not just for butterflies 

But it is not only monarchs that take nourishment and shelter in the milkweeds; many species of butterflies can be found just by observing one patch of plants. First, inspect the flowers: they are really quite beautiful in shape and form, and they can be very fragrant when they first bloom . Bees and wasps of all kinds are attracted to the beautiful flowers and abundant nectar as well. Inspect the leaves. Tell-tale signs of a caterpillar at work are the chewing patterns and holes in the leaves. Monarch caterpillars seem to make small holes right in the leaf as they get going. Other insects will nibble edges or the tips as instead. They also excrete a lot of waste, called frass, as they eat and digest. A real good sign of a caterpillar. Be on the look-out for other insects as well. Aphids of several colors are frequently found covering parts of the stems. They suck plant juices and excrete a sweet “honeydew” liquid that attracts ants. Ants are frequent climbers of milkweed stems as they tend to their aphid farm. Another very common find is the red milkweed beetle. They look like an elongated ladybug with extra long antennae. They like being up near the tips of the plant and are quick to drop to the ground when disturbed. If you feel like being brave ( they don’t bite), pick one of them up between your fingers and hold up to your ear-they make a squeaky-clicky noise. There are leafhoppers, snow crickets, and numerous kinds of flies that visit the milkweeds. One non-insect that I have noticed more recently is a snail, a small air breathing land snail, part of the amber snail family; these are likely European. I have discovered quite a number of them cruising , if you can call it that, along the leaves and stems of milkweed. I don’t remember them from my childhood.
Aphid colonies suck on the plant's juices then secrete a sweet liquid that in turn attracts ants.

As a full-sized caterpillar eats, it leaves behind tell-tale frass.

The red milkweed beetle is easy to identify with its bright color and black spots.

 Milkweed abounds 

The Knox Preserve and Preston Nature Preserve are two of the best places to easily find all kinds of milkweed along the trails. While I was moving through the big patch at Knox, I managed to trip into a well-disguised woodchuck hole, and as I tumbled awkwardly, I scared a rabbit out of hiding. With attention to the little things, you may be surprised at the variety of wildlife you will find associated with milkweeds.
Air breathing amber snails are now common on milkweed plants.

Can't beat the beauty of a red-banded leaf hopper.

Photographs by Beth Sullivan.