It isn’t always easy to tell the good guys from the bad guys.

Roxanne Ackerman of Aquinnah (definitely one of the good ones) called last week to find out about a mass of insects that were voraciously eating the seedpods of her milkweed plants. She wanted to know whether they were good or bad?

Her description of the location of the insects (on the milkweed seed pods) and their physical characteristics (masses of red/orange bugs with black dots) made the identification of milkweed bugs easy. In their case, however, it is not clear-cut whether they are villains or heroes.  

Milkweed bugs are ‘true bugs’ in the order Hemipteran, so it is entomologically acceptable to call them bugs. As adults they have striking black and orange X-shaped patterns on their backs and are easily observed in each of the stages on milkweed plants. Eggs will be laid and four instars (life-stages) of larvae will morph into adults in 28 to 30 days. Since larvae eat the seeds of milkweed, you see them in the late summer after the milkweed pods have formed and seeds ripened.

Known as the monarch’s plant, milkweed is essential for the survival of this notable butterfly. Monarchs, however, are not the only species that use milkweeds. Many other insects find home and hearth on milkweed; these include milkweed beetles, a few varieties of aphids, spider mites, tussock moth caterpillars, and those milkweed bugs. After all, it is a jungle out there!

Doug Tallamy, author and native plant advocate, believed this about the role of plants: “A plant that has fed nothing has not done its job.” The aforementioned insects use milkweed for food as well as habitat, and so could be considered competition for monarchs. And since the milkweed bugs eat the seeds of the plant, they do limit the spread of seeds and thus discourage the expansion of this important species.

Two questions thus emerge. 

The first is whether this insect is in ecological balance with the milkweed — that is, whether it will harm or kill the milkweed efficiently enough to destroy the entire population of the plant in any given locale?

In the case of the milkweed bug, this critter is more of a nuisance than a threat to the plant if the plant’s population is robust enough to survive a milkweed bug onslaught. Because it eats the seeds, the bug affects seed dispersal and thus the plant’s ability to increase its range, but this does not necessarily bring about the demise of the plant or the field of plants.  

The second concern is whether there is enough milkweed for everyone? Will the monarch’s food and habitat needs be affected by these others pests? If there are many milkweed plants, there might be room for everyone. However, if there are only a few plants, or if the infestation of milkweed bugs is extensive, it might be wise to reduce the bug’s population. Yet, as we’ve learned, there are other insects that might be glad to take over the milkweed bug’s niche.

A female milkweed bug can produce 2,000 eggs in her lifetime. These eggs hatch into the mass of larvae that Roxanne observed on her milkweed seedpods. If all of your milkweeds pods are covered, it might be time to take action. Though there are chemical treatments, I won’t make that recommendation. Instead, take the infected pods and dip them in a bowl of soapy water. That will remove the pests and leave the plants to finish their growth cycle.

Rodney King famously inquired, “Can’t we all get along?”  In the case of these pests (a name they may or may not deserve) maybe is the answer. My advice to Roxanne is to assess the severity of the infestation and decide whether those milkweed bugs will negatively affect the population of milkweed plants or inhibit the plant’s ability to provide for monarchs. Like so many things in science, and in life, determining the good guys from the bad guys is not always crystal clear.

Suzan Bellincampi is director of the Felix Neck Wildlife Sanctuary in Edgartown, and author of Martha’s Vineyard: A Field Guide to Island Nature.